Forme is a HTML forms library for ruby with the following goals:

1. Have no external dependencies

2. Have a simple API

3. Support forms both with and without related objects

4. Allow compiling down to different types of output

5. Integrate easily into web frameworks

Forme is designed to make creating HTML forms easier. Flexibility and ease of use are the primary objectives. Here’s a basic example, showing usage without a related object:

Forme.form({:action=>'/foo'}) do |f|
  f.input(:text, :name=>'bar')
  f.tag(:fieldset) do
    f.input(:textarea, :name=>'baz')
  end
 f.button('Update')
end

This results in the following HTML:

<form action="/foo">
  <input name="bar" type="text"/>
  <fieldset>
    <textarea name="baz"></textarea>
  </fieldset>
  <input type="submit" value="Update"/>
</form>

Forme also supports forms that are associated with objects, and has specific support for Sequel::Model objects to allow easily building forms for such objects. The Sequel support handles inputs based on database columns, and automatically handles labels and errors:

Forme.form(Album[1], action: '/foo') do |f|
  f.input :name
  f.input :copies_sold
end

This results in the following HTML:

<form action="/foo" method="post">
  <label>Name:
    <input id="album_name" name="album[name]" type="text" value="Rising Force"/>
  </label>
  <label>Copies Sold:
    <input id="album_copies_sold" inputmode="numeric" name="album[copies_sold]" pattern="-?[0-9]*" type="text" value="100000"/>
  </label>
</form>

In addition to integrating with Sequel, Forme also integrates into three separate web frameworks, Roda, Rails, and Sinatra, allowing use of forms inside templates. This is the most common usage of Forme.

One distinct advantage of Forme over other form libraries is the use of an abstract syntax tree internally, allowing the same form code to compile to different HTML with different options. For example, it allows using the exactly same form code to display a form you can modify as well as a read-only view, just by passing a single option when creating the form. For example, with the first example in this section, if you pass the formatter: :readonly option, you get the following HTML instead:

<form action="/foo">
  <span class="readonly-text"></span>
  <fieldset>
    <div class="readonly-textarea"></div>
  </fieldset>
</form>

This allows you to reuse the same form code in multiple contexts, which can save considerable development time.

gem install forme

Demo Site

forme-demo.jeremyevans.net

RDoc

forme.jeremyevans.net

Source

github.com/jeremyevans/forme

Discussion Forum

github.com/jeremyevans/forme/discussions

Bug Tracker

github.com/jeremyevans/forme/issues

While not typically done, you can instantiate Forme::Form objects directly and use them:

f = Forme::Form.new
f.open(:action=>'/foo', :method=>:post) # '<form action="/foo" method="post">'
f.input(:textarea, :value=>'foo', :name=>'bar') # '<textarea name="bar">foo</textarea>'
f.input(:text, :value=>'foo', :name=>'bar') # '<input name="bar" type="text" value="foo"/>'
f.close # '</form>'

With an object, Form#input calls forme_input on the obj with the form, field, and options, which should return a Forme::Input or Forme::Tag instance. Also, in Form#initialize, forme_config is called on object with the form if the object responds to it, allowing customization of the entire form based on the object.

f = Forme::Form.new(obj)
f.input(:field) # '<input id="obj_field" name="obj[field]" type="text" value="foo"/>'

If the object doesn’t respond to forme_input, it falls back to creating text fields with the name and id set to the field name and the value set by calling the given method on the object (or using #[] if the object is a hash).

f = Forme::Form.new([:foo])
f.input(:first) # '<input id="first" name="first" type="text" value="foo"/>'

Forme.form takes up to 3 arguments, and yields the Forme::Form object to the block (if given). Here are the argument styles that you can use for Forme.form.

No args

Creates a Form object with no options and not associated to an obj, and with no attributes in the opening tag.

1 hash arg

Treated as opening form tag attributes, creating a Form object with no options.

1 non-hash arg

Treated as the Form‘s obj, with empty options and no attributes in the opening tag.

2 hash args

First hash is opening attributes, second hash is Form options.

1 non-hash arg, 1-2 hash args

First argument is Form‘s obj, second is opening attributes, third if provided is Form’s options.

Examples:

# No arguments
Forme.form 

# 1 hash argument (attributes)
Forme.form(action: '/foo')

# 1 non-hash argument (a reference object used when building the form)
Forme.form(Album[1])

# 2 hash arguments (attributes, and options)
Forme.form({action: '/foo'}, values: params)

# 1 non-hash argument, 1-2 hash arguments (ref obj, attributes, options)
Forme.form(Album[1], action: '/foo')
Forme.form(Album[1], {action: '/foo'}, values: params)

If you want a Forme::Form instance where the reference object is a Hash, then you need to pass the hash object using the :obj option:

Forme.form({action: '/foo'}, obj: {foo: 'bar'})

You can also create Forme::Form objects the normal ruby way using Forme::Form#new. The difference between Forme::Form#new and Forme.form is that Forme.form includes the enclosing <form> tag, where Forme::Form#new does not. Because of this, Forme::Form does not accept a hash of <form> tag attributes, so it has the following API:

# No arguments
Forme::Form.new

# 1 hash argument
Forme::Form.new(values: params)

# 1 non-hash argument
Forme::Form.new(Album[1])

# 1 non-hash argument, 1-2 hash arguments
Forme::Form.new(Album[1], values: params)

If you create a Form via Forme::Forme#new, you can use the form method to create a form tag:

f = Forme::Form.new
f.form(action: '/foo')

This is what Forme.form uses internally to create the +<form>+ tag

This adds an input to the form. If the form has an associated object, and that object responds to forme_input, calls forme_input with the argument and options:

f = Forme::Form.new(obj)
f.input(:field) # '<input id="obj_field" name="obj[field]" type="text" value="foo"/>'

If the form has an associated object, and that object does not respond to forme_input, calls the method on the object (or uses [] if the object is a hash), and uses the result as the value for a text input:

f = Forme::Form.new([:foo])
f.input(:first) # '<input id="first" name="first" type="text" value="foo"/>'

If the object does not respond to forme_input, you can change the type of the input via the :type option:

f = Forme::Form.new(obj)
f.input(:field, :type=>:email) # '<input id="obj_field" name="obj[field]" type="email" value="foo"/>'

If the form does not have an associated object, the first argument is used as the input type:

f = Forme::Form.new
f.input(:text) # '<input type="text" />'

The second argument is an options hash. See below for the supported input types and options.

This adds a tag to the form. If a block is given, yields to the block, and tags and inputs inside the block are placed inside the tag. The first argument is the type of tag to create, and the second argument if given should be a hash of tag attributes. This allows you to nest inputs inside tags:

Forme.form do |f|
  f.tag(:span, :class=>"foo") do
    f.input(:text)
  end
end

Which results in a form similar to the following:

<form>
  <span class="foo">
    <input type="text"/>
  </span>
</form>

This wraps multiple inputs in a tag (it uses the :inputs_wrapper transformer discussed below, so it uses a fieldset by default). You can give the inputs to add as an enumerable argument:

f.inputs([:textarea, [:text, :value=>'a']])
# <fieldset>
#   <textarea></textarea>
#   <input type="text" value="a"/>
# </fieldset>

You can also provide a block:

f.inputs([:textarea]) do
  f.input(:text, :value=>'a')
end

Any options given are passed to the inputs_wrapper (so you can use options such as :legend to set a legend for the fieldset), and also to the with_opts method (so you can use options such as :wrapper to modify the default wrapper transformer for inputs inside the block). There is also one option specific to the inputs method:

:nested_inputs_wrapper

Sets the default inputs_wrapper to use for calls to inputs inside the block. The reason for this option is that :inputs_wrapper option affects the current call to inputs, so if you want to use a different inputs_wrapper for nested calls, you need this option.

This adds a submit input to the form:

f.button
# <input type="submit"/>

It can be called with a string to provide a value for the button:

f.button('Search')
# <input type="submit" value="Search"/>

It can be called with a hash to provide options for the submit input:

f.button(value: 'Search', class: 'btn')
# <input class="btn" type="submit" value="Search"/>

This requires a block, and modifies the Forme::Form’s options inside the block, restoring the options when the block returns:

f.input(:text)
# <input type="text"/>

f.with_opts(wrapper: :li) do
  f.input(:text)
end
# <li><input type="text"/></li>

This supports most options you can provide to Forme::Form, but not all.

This uses with_opts to change the Forme::Form object temporarily. It yields the object to the block, and also supports appending to the existing namespaces:

Forme.form([:foo], {action: '/path'}, namespace: 'a') do |f|
  f.input(:first)
  # <input id="a_first" name="a[first]" type="text" value="foo"/>
  f.with_obj(['foobar'], 'b') do |o|
    f.input(:first, :size=>o.first.size)
    # <input id="a_b_first" name="a[b][first]" size="6" type="text" value="foobar"/>
  end
end

This allows you to provide an object-yielding enumerable. each_object will call with_obj with each object in the enumerable. It yields each object as well as the index of the object in the enumerable, and includes the index in the namespace:

objectlist = [['foobar'], ['good']]
Forme.form([:foo], :namespace=>'a') do |f|
  f.each_obj(objectlist, 'b') do |o, i|
    f.input(:first, :size=>10+i)
  end
  # <input id="a_b_0_first" name="a[b][0][first]" size="10" type="text" value="foobar"/>
  # <input id="a_b_1_first" name="a[b][1][first]" size="11" type="text" value="good"/>
end

Forme ships with a Sequel plugin (use Sequel::Model.plugin :forme to enable), that makes Sequel::Model instances support the forme_config and forme_input methods and return customized inputs. An additional instance method, forme_namespace can optionally be defined to customize how model classnames are transformed into form classes and input IDs and names. This can be useful if your Sequel::Model classes are nested under a parent namespace. The default namespace uses Sequel::Model#underscore.

module Admin
  class Albums < Sequel::Model
    def forme_namespace
      self.class.name.underscore.tr('/', '_')
    end
  end
end

The Sequel :forme plugin also integerates with Sequel’s validation reflection support that comes with the Sequel validation_class_methods plugin. It will add pattern and maxlength attributes based on the format, numericality, and length validations.

In addition to the default Forme options, the Sequel support includes, for specific column types, these additional options to the #input method:

:as

Can be set to :select, :radio, or :checkbox. :select will use a select input with three options, a blank option, a true option, and a false option. :radio will use two radio inputs, one for true and one for false. :checkbox will use a single checkbox input. By default, uses :select if NULL values are allowed and the option is not required, and :checkbox otherwise.

:false_label

The value to use for the false label, ‘No’ by default.

:false_value

The value to use for the false input, ‘f’ by default.

:true_label

The value to use for the true label, ‘Yes’ by default.

:true_value

The value to use for the true input, ‘t’ by default.

:as

Can be set to :textarea to use a textarea input. You can use the usual attributes hash or a stylesheet to control the size of the textarea.

The Sequel support also handles associations, allowing you to change which objects are associated to the current object.

Forme.form(Album[1], :action=>'/foo') do |f|
  f.input :name
  f.input :artist
  f.input :tags, :as=>:checkbox
end

This will create a form similar to:

<form action="/foo" method="post">
  <label>Name: <input id="album_name" name="album[name]" type="text" value="Blue Hawaii"/></label>
  <label>Artist: <select id="album_artist_id" name="album[artist_id]">
    <option selected="selected" value="1">Elvis Presley</option>
    <option value="2">The Beatles</option>
    <option value="3">The Monkeys</option>
  </select></label>
  <span class="label">Tags:
    <label><input checked="checked" id="album_tag_pks_1" name="album[tag_pks][]" type="checkbox" value="1"/> Rock and Roll</label>
    <label><input id="album_tag_pks_2" name="album[tag_pks][]" type="checkbox" value="2"/> Blues</label>
    <label><input id="album_tag_pks_3" name="album[tag_pks][]" type="checkbox" value="3"/> Country</label>
  </span>
</form>

For one_to_many and many_to_many associations, you will probably want to use the association_pks plugin that ships with Sequel.

This also supports the pg_array_to_many association type that comes with Sequel’s pg_array_association plugin.

association input options:

:as

For many_to_one associations, set to :radio to use a series of radio buttons instead a select input. For one_to_many, many_to_many, and pg_array_to_many associations, set to :checkbox to use a series of checkboxes instead of a multiple select input.

:dataset

If a Dataset, uses the dataset to retrieve the options. If a Proc or Method, calls the proc or method with the default dataset, and should return a modified dataset to use.

:options

Specify the options to use for the input(s), instead of querying the database.

:name_method

If a String or Symbol, treats it as a method name and calls it on each object returned by the dataset to get the text to use for the option. If not given, tries the following method names in order: :forme_name, :name, :title, :number. If given and not a String or Symbol, a callable object is assumed, and the value is called with each object and should return the text to use for the option.

The Sequel support includes a method called subform, which can handle nested_attributes:

Forme.form(Album[1], :action=>'/foo') do |f|

  f.input :name

  f.subform :artist do
    f.input :name
  end

  f.subform :tracks do
    f.input :number
    f.input :name
  end

end

This adds an input for editing the artist’s name after the album’s inputs, as well as inputs for editing the number and name for all of the tracks in the album, creating a form similar to:

<form action="/foo" method="post">

  <label>Name: <input id="album_name" name="album[name]" type="text" value="Blue Hawaii"/></label>

  <input id="album_artist_attributes_id" name="album[artist_attributes][id]" type="hidden" value="1"/>
  <fieldset class="inputs"><legend>Artist</legend>
    <label>Name: <input id="album_artist_attributes_name" name="album[artist_attributes][name]" type="text" value="Elvis Presley"/></label>
  </fieldset>

  <input id="album_tracks_attributes_0_id" name="album[tracks_attributes][0][id]" type="hidden" value="1"/>
  <fieldset class="inputs"><legend>Track #1</legend>
    <label>Number: <input id="album_tracks_attributes_0_number" inputmode="numeric" name="album[tracks_attributes][0][number]" pattern="-?[0-9]*" type="text" value="1"/></label>
    <label>Name: <input id="album_tracks_attributes_0_name" name="album[tracks_attributes][0][name]" type="text" value="Blue Hawaii"/></label>
  </fieldset>
  <input id="album_tracks_attributes_1_id" name="album[tracks_attributes][1][id]" type="hidden" value="2"/>
  <fieldset class="inputs"><legend>Track #2</legend>
    <label>Number: <input id="album_tracks_attributes_1_number" inputmode="numeric" name="album[tracks_attributes][1][number]" pattern="-?[0-9]*" type="text" value="2"/></label>
    <label>Name: <input id="album_tracks_attributes_1_name" name="album[tracks_attributes][1][name]" type="text" value="Almost Always True"/></label>
  </fieldset>

</form>

Note: blank lines added for clarity; they would not appear in the actual output

subform options:

:inputs

Automatically call inputs with the given values. Using this, it is not required to pass a block to the method, though it will still work if you do.

:inputs_opts

When using the :grid option, this allows you to specify options to pass to the table InputsWrapper.

:legend

Overrides the default :legend used (which is based on the association name). You can also use a proc as the value, which will called with each associated object (and the position in the associated object already for *_to_many associations), and should return the legend string to use for that object.

:grid

Sets up a table with one row per associated object, and one column per field.

:labels

When using the :grid option, override the labels that would be created via the :inputs option. If you are not providing an :inputs option or are using a block with additional inputs, you should specify this option.

:skip_primary_key

Skip adding a hidden primary key field for existing objects.

The Sequel forme plugin only handles creating the forms, it does not handle processing input submitted via forms. For a form such as:

Forme.form(Album[1], :action=>'/foo') do |f|
  f.input :name
  f.input :copies_sold
end

Input of the form will often be submitted as the following parameter hash (this depends on your web framework, but Rack works this way by default):

{'album'=>{'name'=>'Rising Force', 'copies_sold'=>'100000'}}

One way to handle the form submission is to use Sequel::Model#set_fields.

album = Album[1]
album.set_fields(params['album'], %w'name copies_sold')
album.save

Note that you have to specify the parameter names again as the second argument to set_fields.

Handling submitted parameters becomes more complex as your forms become more complex. For example, if you are only displaying certain form fields in certain situations:

album = Album[1]
Forme.form(album, :action=>'/foo') do |f|
  f.input :name
  f.input :copies_sold if album.released?
end

Then your parameter handling becomes more complex:

album = Album[1]
album.set_fields(params['album'], %w'name')
album.set_fields(params['album'], %w'copies_sold') if album.released?
album.save

As you can see, you basically need to recreate the conditionals used when creating the form, so that that the processing of the form submission handles only the inputs that were displayed on the form.

The Sequel forme_set plugin is designed to make handling form submissions easier. What it does is record the form fields that are used on the object, and then it uses those fields to handle input submitted for the object. For example:

album = Album[1]
Forme.form(album, :action=>'/foo') do |f|
  f.input :name
  f.input :copies_sold if album.released?
end
album.forme_set(params['album'])

If the album has been released, and the form would display the name and copies_sold inputs, then forme_set will accept input for both. If the album has not been released, the form will only display the name input, so forme_set will only accept the name input.

So forme_set offers two advantages over using set_fields:

1. DRYs up code as you don’t have to specify the names twice

2. Simplifies complex form submissions by eliminating duplication of conditionals

forme_set offers one additional advantage over using set_fields. When dealing with associations, set_fields does not check that the value submitted for an input matches one of the available options displayed on the form. For example, if you have a form such as:

Forme.form(album, :action=>'/foo') do |f|
  f.input :name
  f.input :artist, :dataset=>proc{|ds| ds.where{name > 'M'}}
end

The form will only display artists whose name is greater than ‘M’. However, if you process input using:

album.set_fields(params['album'], %w'name artist_id')

Then a malicious user can submit an artist_id for an artist whose name is not greater than ‘M’, and the value will be set. In addition to setting values, forme_set also adds validations that the submitted values for associated objects match one of the options displayed on the form, which can increase security.

Because forme_set relies on creating form inputs using the same model instance that will be used for accepting input, using it often requires some code rearranging. If you are storing Forme::Form objects and later using them on forms, it is fairly simple to move the Forme::Forme object creation to a method, that you can call both in the initial display and when processing the input:

def album_form(album)
  Forme.form(album, :action=>'/foo') do |f|
    f.input :name
    f.input :copies_sold
  end
end

Then when displaying the form:

<%= album_form(Album[1]) %>

and when processing the form’s input:

album = Album[1]
album_form(album)
album.forme_set(params['album'])

However, if you use Forme’s ERB/Rails template integration (see below), and are inlining forms in your templates, unless you want to extract the Forme::Form creation to methods, you have to basically rerender the template when processing the input. How you do this is specific to the web framework you are using, but is it similar to:

@album = Album[1]
render :template
@album.forme_set(params['album'])

forme_set is not perfect, there are ways to use Forme that forme_set will not handle correctly. First, forme_set only works with forms that use model objects, and doesn’t handle inputs where the :obj option is provided to change the input. Additionally, forme_set does not currently handle subform/nested_attributes.

In cases where forme_set does not handle things correctly, you can use forme_parse, which will return metadata that forme_set uses (forme_set calls forme_parse internally). forme_parse returns a hash with the following keys:

:values

A hash of values that can be used to update the model, suitable for passing to Sequel::Model#set.

:validations

A hash of values suitable for merging into forme_validations. Used to check that the submitted values for associated objects match one of the options for the input in the form.

It is possible to use forme_set for the forms it can handle, and use forme_parse and set_fields for other forms.

The Roda forme_set plugin builds on the Sequel forme_set plugin and is designed to make handling form submissions even easier. This plugin adds a hidden form input to store which fields were used to build the form, as well as some other metadata. It adds another hidden form input with an HMAC, so that on submission, if the HMAC matches, you can be sure that an attacker didn’t add extra fields.

There are a couple advantages to this plugin over using just the Sequel forme_set plugin. One is that you do not need to record the form fields when processing the submission of a form, since the information you need is included in the form submission. Another is that calling the forme_set method is simpler, since it can determine the necessary parameters.

While you need code like this when using just the Sequel forme_set plugin:

album = Album[1]
Forme.form(album, :action=>'/foo') do |f|
  f.input :name
  f.input :copies_sold if album.released?
end
album.forme_set(params['album'])

when you also use the Roda forme_set plugin, you can simplify it to:

album = Album[1]
forme_set(album)

The Roda forme_set plugin supports and uses the same validations as the Sequel forme_set plugin. However, the Roda plugin is more accurate because it uses the options that were present on the form when it was originally built, instead of the options that would be present on the form when the form was submitted. However, note that that can be a negative if you are dynamically adding values to both the database and the form between when the form was built and when it was submitted.

Because the Roda forme_set plugin includes the metadata needed to process the form in form submissions, you don’t need to rearrange code to use it, or rerender templates. You can do:

album = Album[1]
forme_set(album)

And the method will update the album object using the appropriate form values.

Note that using the Roda forme_set plugin requires you set a secret for the HMAC. It is important that you keep this value secret, because if an attacker has access to this, they would be able to set arbitrary attributes for model objects. In your Roda class, you can load the plugin via:

plugin :forme_set, :secret => ENV["APP_FORME_HMAC_SECRET"]

By default, invalid form submissions will raise an exception. If you want to change that behavior (i.e. to display a nice error page), pass a block when loading the plugin:

plugin :forme_set do |error_type, obj|
  # ...
end

The block arguments will be a symbol for the type of error (:missing_data, :missing_hmac, :hmac_mismatch, :csrf_mismatch, or :missing_namespace) and the object passed to forme_set. This block should raise or halt. If it does not, the default behavior of raising an exception will be taken.

The Roda forme_set plugin supports form versions. This allows you to gracefully handle changes to forms, processing submissions of the form generated before the change (if possible) as well as the processing submissions of the form generated after the change.

For example, maybe you have an existing form with just an input for the name:

form(album) do |f|
  f.input(:name)
end

Then later, you want to add an input for the number of copies sold:

form(album) do |f|
  f.input(:name)
  f.input(:copies_sold)
end

Using the Roda forme_set plugin, submissions of the old form would only set the name field, it wouldn’t set the copies_sold field, since when the form was created, only the name field was used.

You can handle this case be versioning the form when making changes to it:

form(album, {}, :form_version=>1) do |f|
  f.input(:name)
  f.input(:copies_sold)
end

When you are processing the form submission with forme_set, you pass a block, which will be yielded the version for the form (nil if no version was set):

forme_set(album) do |version|
  if version == nil
    album.copies_sold = 0
  end
end

The block is also yielded the object passed for forme_set, useful if you don’t keep a reference to it:

album = forme_set(Album.new) do |version, obj|
  if version == nil
    obj.copies_sold = 0
  end
end

You only need to support old versions of the form for as long as their could be active sessions that could use the old versions of the form. As long you as are expiring sessions to prevent session fixation, you can remove the version handling after the expiration period has passed since the change to the form was made.

Note that this issue with handling changes to forms is not specific to the Roda forme_set plugin, it affects pretty much all form submissions. The Roda forme_set plugin just makes this issue easier to handle.

The Roda forme_set plugin has basically the same caveats as Sequel forme_set plugin. Additionally, it has a couple other restrictions that the Sequel forme_set plugin does not have.

First, the Roda forme_set plugin only handles a single object in forms, which must be provided when creating the form. It does not handle multiple objects in the same form, and ignores any fields set for an object different from the one passed when creating the form. You can use the Sequel forme_set plugin to handle form submissions involving multiple objects, or for the objects that were not passed when creating the form.

Second, the Roda forme_set plugin does not handle cases where the field values are placed outside the form’s default namespace. The Sequel forme_set plugin can handle those issues, as long as all values are in the same namespace, since the Sequel forme_set plugin requires you pass in the specific hash to use (the Roda forme_set plugin uses the form’s namespace information and the submitted parameters to determine the hash to use).

In cases where the Roda forme_set does not handle things correctly, you can use forme_parse, which will return metadata in the same format as the Sequel plugin forme_parse method, with the addition of a :form_version key in the hash for the form version.

It is possible to use the Roda forme_set plugin for the submissions it can handle, the Sequel forme_set plugin for the submissions it can handle, and set other fields manually using the Sequel set_fields methods.

Note that when using the Roda forme_set plugin with an existing form, you should first enable the Roda plugin without actually using the Roda forme_set method. Do not start using the Roda forme_set method until all currently valid sessions were established after the Roda forme_set plugin was enabled. Otherwise, sessions that access the form before the Roda forme_set plugin was enabled will not work if they submit the form after the Roda forme_set plugin is enabled.

In addition to the Sequel plugins mentioned above, Forme also ships with additional Sequel plugins:

forme_i18n

Handles translations for labels using i18n.

Forme ships with multiple Roda plugins

• forme_set (discussed above)

• forme

• forme_route_csrf

• forme_erubi_capture_block

• forme_erubi_capture

For new code, it is recommended to use forme_route_csrf, as that uses Roda’s route_csrf plugin, which supports more secure request-specific CSRF tokens. In both cases, usage in ERB templates is the same:

<% form(@obj, action: '/foo') do |f| %>
  <%= f.input(:field) %>
  <% f.tag(:fieldset) do %>
    <%= f.input(:field_two) %>
  <% end %>
<% end %>

The forme_route_csrf plugin’s form method supports the following options in addition to the default Forme.form options:

:emit

Set to false to not emit implicit tags into template. This should only be used if you are not modifying the template inside the block.

:csrf

Set to force whether a CSRF tag should be included. By default, a CSRF tag is included if the form’s method is one of the request methods checked by the Roda route_csrf plugin.

:use_request_specific_token

Set whether to force the use of a request specific CSRF token. By default, uses a request specific CSRF token unless the Roda route_csrf plugin has been configured to support non-request specific tokens.

The emit: false option allows you to do:

<%= form(@obj, {action: '/foo'}, emit: false) do |f|
  f.input(:field)
  f.tag(:fieldset) do
    f.input(:field_two)
  end
end %>

This is useful if you are calling some method that calls form with a block, where the resulting entire Forme::Forme object will be literalized into the template. The form will include the CSRF token and forme_set metadata as appropriate.

The forme plugin does not require any csrf plugin, but will transparently use Rack::Csrf if it is available. If Rack::Csrf is available a CSRF tag if the form’s method is POST, with no configuration ability.

The forme_erubi_capture_block plugin builds on the forme_route_csrf plugin, but it supports the erubi/capture_block engine, which allows this syntax:

<%= form(@obj, :action=>'/foo') do |f| %>
  <%= f.input(:field) %>
  <%= f.tag(:fieldset) do %>
    <%= f.input(:field_two) %>
  <% end %>
<% end %>

If you use the forme_erubi_capture)block plugin, you need to manually set Roda to use the erubi/capture_block engine, which you can do via:

require 'erubi/capture_block'
app.plugin :render, :engine_opts=>{'erb'=>{:engine_class=>Erubi::CaptureBlockEngine}}

The forme_erubi_capture plugin requires Erubi 1.13.0+.

The forme_erubi_capture plugin builds on the forme_route_csrf plugin, but it supports the erubi/capture_end engine, which allows this syntax:

<%|= form(@obj, :action=>'/foo') do |f| %>
  <%= f.input(:field) %>
  <%|= f.tag(:fieldset) do %>
    <%= f.input(:field_two) %>
  <%| end %>
<%| end %>

If you use the forme_erubi_capture plugin, you need to manually set Roda to use the erubi/capture_end engine, which you can do via:

require 'erubi/capture_end'
app.plugin :render, :engine_opts=>{'erb'=>{:engine_class=>Erubi::CaptureEndEngine}}

The forme_erubi_capture plugin requires Roda 3.50.0+.

Forme ships with a Sinatra extension that you can get by require "forme/erb" and using including Forme::ERB::Helper. This is tested to support ERB templates in Sinatra. It allows you to use the following API in your erb templates:

<% form(@obj, :action=>'/foo') do |f| %>
  <%= f.input(:field) %>
  <% f.tag(:fieldset) do %>
    <%= f.input(:field_two) %>
  <% end %>
<% end %>

In order to this to work transparently, the ERB outvar needs to be @_out_buf (this is the default in Sinatra). The Sinatra extension also supports the emit: false option to not directly modify the related template (see example in the Roda section for usage).

Forme ships with a Rails extension that you can get by require "forme/rails" and using helper Forme::Rails::ERB in your controller. If allows you to use the following API in your Rails forms:

<%= forme(@obj, :action=>'/foo') do |f| %>
  <%= f.input(:field) %>
  <%= f.tag(:fieldset) do %>
    <%= f.input(:field_two) %>
  <% end %>
<% end %>

This has been tested on Rails 3.2-7.0.

These are the types and options supported by Forme::Input objects, usually created via Forme::Form#input:

These options are supported by all of the input types:

:attr

The attributes hash to use for the given tag, attributes in this hash take precedence over other options that set attributes.

:autofocus

Set the autofocus attribute if true

:class

A class to use. Unlike other options, this is combined with the classes set in the :attr hash.

:dasherize_data

Automatically replace underscores with hyphens for symbol data attribute names in the :data hash. Defaults to false.

:data

A hash of data-* attributes for the resulting tag. Keys in this hash will have attributes created with data- prepended to the attribute name.

:disabled

Set the disabled attribute if true

:error

Set an error message, invoking the error_handler

:error_handler

Set a custom error_handler, overriding the form’s default

:help

Set help text to use, invoking the helper

:helper

Set a custom helper, overriding the form’s default

:id

The id attribute to use

:key

The base to use for the name and id attributes, based on the current namespace for the form.

:label

Set a label, invoking the labeler

:labeler

Set a custom labeler, overriding the form’s default

:name

The name attribute to use

:obj

Set the form object, overriding the form’s default

:placeholder

The placeholder attribute to use

:required

Set the required attribute if true

:type

Override the type of the input when the form has an associated object but the object does not respond to forme_input

:value

The value attribute to use for input tags, the content of the textarea for textarea tags, or the selected option(s) for select tags.

:wrapper

Set a custom wrapper, overriding the form’s default

Creates an input tag with type checkbox, as well as a hidden input tag. Options:

:checked

Mark the checkbox as checked.

:hidden_value

The value to use for the hidden input tag.

:no_hidden

Don’t create a hidden input tag.

Creates an input tag with type radio. Options:

:checked

Mark the radio button as checked.

By default, creates an input tag with type date or datetime. With the as: :select option, creates multiple select options. Options:

:as

When value is :select, uses 3 or 6 select boxes by default.

:order

The order of select boxes when using as: :select. Entries should be a symbol for the select field and string to use a string (:date default: [:year, '-', :month, '-', :day]) (:datetime default: [:year, '-', :month, '-', :day, ' ', :hour, ':', :minute, ':', :second])

:select_labels

The labels to use for the select boxes. Should be a hash keyed by the symbol used (e.g. {:month=>'Month'}). By default, no labels are used.

:select_options

The options to use for the select boxes. Should be a hash keyed by the symbol used in order (e.g. {:year=>1970..2020}). The values can be a number used as both the value and the text of the option or an array with two elements, the first of which is the value for the option and the second of which is the text for the option.

Creates a select tag, containing option tags specified by the :options option. Options:

:add_blank

Add a blank option if true. If the value is a string, use it as the text content of the blank option. The default value can be set with Forme.default_add_blank_prompt, and defaults to the empty string.

:blank_attr

If :add_blank is set, sets the attributes to use for the blank option.

:blank_position

If :add_blank is set, can be set to :after to add the prompt after the inputs, instead of before (which is the default).

:multiple

Creates a multiple select box.

:optgroups

An enumerable of pairs with the first element being option group labels or a hash of option group attributes, and values being enumerables of options (as described by :options below). Creates optgroup tags around the appropriate options. This overrides any options specified via :options.

:options

An enumerable of options used for creating option tags. If the :text_method and :value_method are not given and the entry is an array, uses the first entry of the array as the text of the option, and the last entry of the array as the value of the option. If the last entry of the array is a hash, uses the hash as the attributes for the option. If the option value is :hr, uses an hr tag (allowed in recent versions of the HTML standard).

:selected

The value that should be selected. Any options that are equal to this value (or included in this value if a multiple select box), are set to selected.

:size

Uses the size attribute on the tag

:text_method

If set, each entry in the array has this option called on it to get the text of the object.

:value

Same as :selected, but has lower priority.

:value_method

If set (and :text_method is set), each entry in the array has this method called on it to get the value of the option.

Creates a set of checkbox inputs all using the same name. Supports the same options as the :select type, except that the :multiple option is assumed to be true. Also supports the following options:

:tag_wrapper

The wrapper transformer for individual tags in the set

:tag_labeler

The labeler transformer for individual tags in the set

:tag_label_attr

The attributes to use for labels for individual tags in the set

Creates a set of radio buttons all using the same name. Supports the same options as the :checkboxset type.

Creates a textarea tag. Options:

:cols

The number of columns in the text area.

:rows

The number of rows in the text area.

:maxlength

Use the maxlength attribute on the tag

:minlength

Use the minlength attribute on the tag

Creates an input tag with the given type. This makes it easy to use inputs such as text and password, as well as newer HTML5 inputs such as number or email. Options:

:size

Uses the size attribute on the tag

:maxlength

Use the maxlength attribute on the tag

:minlength

Use the minlength attribute on the tag

These are the options supported by Forme::Form object, mostly used to set the defaults for Inputs created via the form:

:after

A callable object that is yielded the Form instance after yielding to the block. Can be used to add hidden inputs to the end of the form.

:before

A callable object that is yielded the Form instance before yielding to

the block. Can be used to add hidden inputs to the start of the form.

:config

The configuration to use, which automatically sets defaults for the transformers to use.

:errors

A Hash of errors from a previous form submission, used to set default errors for inputs when the inputs use the :key option.

:error_handler

Sets the default error_handler for the form’s inputs

:helper

Sets the default helper for the form’s inputs

:formatter

Sets the default formatter for the form’s inputs

:input_defaults

Sets the default options for each input type. This should be a hash with input type keys, where the values are the hash of default options to use for the input type.

:inputs_wrapper

Sets the default inputs_wrapper for the form

:labeler

Sets the default labeler for the form’s inputs

:namespace

Sets the default namespace(s) to use for the form. Namespacing will automatically create namespaced name and id attributes for inputs that use the :key option.

:obj

Sets the default obj for the form’s inputs.

:serializer

Sets the serializer for the form

:values

The values from a previous form submission, used to set default values for inputs when the inputs use the :key option.

:wrapper

Sets the default wrapper for the form’s inputs

For forms created by Forme.form, the following options are supported:

:inputs

An array of inputs to create inside the form, before yielding to the block.

:button

A button to add to the form, after yielding to the block.

Internally, Forme builds an abstract syntax tree of objects that represent the form. The abstract syntax tree goes through a series of transformations that convert it from high level abstract forms to low level abstract forms and finally to strings. Here are the main classes used by the library:

Forme::Form

main object

Forme::Input

high level abstract tag (a single Input could represent a select box with a bunch of options)

Forme::Tag

low level abstract tag representing an HTML tag (there would be a separate Tag for each option in a select box)

The difference between Forme::Input and Forme::Tag is that Forme::Tag directly represents the underlying HTML tag, containing a type, optional attributes, and children, while the Forme::Input is more abstract and attempts to be user friendly. For example, these both compile by default to the same select tag:

f.input(:select, :options=>[['foo', 1]])
# or
f.tag(:select, {}, [f.tag(:option, {:value=>1}, ['foo'])])

The group of objects that perform the transformations to the abstract syntax trees are known as transformers. Transformers use a functional style, and all use a call-based API, so you can use a Proc for any custom transformer. The processing of high level Forme::Inputs into raw HTML fragments is performed through the following transformers:

Formatter

converts a Forme::Input instance into a Forme::Tag instance (or array of them).

ErrorHandler

If the Forme::Input instance has a error, takes the formatted tag and marks it as having the error.

Helper

If the Forme::Input instance has any help text, adds the help text in a separate tag.

Labeler

If the Forme::Input instance has a label, takes the formatted output and labels it.

Wrapper

Takes the output of the formatter, labeler, and error_handler transformers, and wraps it in another tag (or just returns it unmodified).

Serializer

converts a Forme::Tag instance into an HTML string.

Technically, only the Serializer is necessary. The Forme::Form#input and Forme::Form#tag methods internally create Input and Tag objects. Before returning results, the input or tag is converted to a string using to_s, which calls the appropriate Serializer. The Serializer calls the appropriate Formatter if it encounters an Input instance, and attempts to serialize the output of that (which is usually a Tag instance). It is up to the Formatter to call the Labeler, ErrorHandler, Helper, and/or Wrapper.

The Forme::Form object takes the transformers as options (:formatter, :labeler, :error_handler, :helper, :wrapper, and :serializer), all of which should be objects responding to call (so you can use Procs) or be symbols registered with the library using Forme.register_transformer:

Forme.register_transformer(:wrapper, :p) do |tag, input|
  input.tag(:p, {}, tag)
end

Most transformers are called with two arguments, tag and input. tag is a Forme::Tag instance, and input is a Forme::Input instance. The Formatter and Serializer transformers are the two exceptions, with Formatter being called with just an input, and Serializer potentionally being called with any object. The Serializer will in general recursively call itself with children of the argument given until a string is returned.

There is also an InputsWrapper transformer, that is called by Forme::Form#inputs. It’s used to wrap up a group of related options (in a fieldset by default). It takes form (Forme::Form instance) and input_opts (Hash) arguments.

Most of the transformers can be overridden on a per instance basis by passing the appropriate option to input or inputs:

f.input(:name, :wrapper=>:p)

Existing transformers can be easily extended (ie, to set the class attribute), by creating your own transformer and then calling the existing transformer.

Forme.register_transformer(:labeler, :explicit) do |tag, input|
  input.opts[:label_attr] ||= { :class => 'label' }
  Forme::Labeler::Explicit.new.call(tag, input)
end

You can override the type of transform for each form or input using the following options:

serializer

tags input/tag, returns string

formatter

takes input, returns tag

error_handler

takes tag and input, returns version of tag with errors noted

helper

takes tag and input, returns version of tag with help added

labeler

takes tag and input, returns labeled version of tag

wrapper

takes tag and input, returns wrapped version of tag

inputs_wrapper

takes form, options hash, and block, wrapping block in a tag

The serializer is the base of the transformations. It turns Tag instances into strings. If it comes across an Input, it calls the formatter on the Input to turn it into a Tag, and then serializes that Tag. The formatter first converts the Input to a Tag, and then calls the labeler if the :label option is set, the error_handler if the :error option is set, and the helper if the :help option is set . Finally, it calls the wrapper to wrap the resulting tag before returning it.

The inputs_wrapper is called by Forme::Form#inputs and serves to wrap a bunch of related inputs.

Forme ships with a bunch of built-in transformers that you can use:

:default

returns HTML strings

:html_usa

returns HTML strings, formats dates and times in American format without timezones

:text

returns plain text strings

:default

turns Inputs into Tags

:disabled

disables all resulting input tags

:readonly

uses span tags for most values, good for printable versions of forms

:after_legend

designed for usage with :legend labeler, putting error message after legend, adding error for first input in the set

:default

modifies tag to add an error class and adds a span with the error message

:set

default error_handler for checkboxset and radioset inputs, that adds an error to the last input in the set

This supports the following options:

:error_attr

A hash of attributes to use for the span with the error message

:default

adds a span with the help text

This supports the following options:

:helper_attr

A hash of attributes to use for the span with the help message

:default

uses implicit labels, where the tag is a child of the label tag

:explicit

uses explicit labels with the for attribute, where tag is a sibling of the label tag

:legend

adds a legend before the tags, mostly useful for accessible checkboxset and radioset inputs

:span

default labeler for checkboxset and radioset inputs that adds a span before the tags

The :default and :explicit labelers respect the following options:

:label_position

Can be set to :before or :after to place the label before or after the the input.

:label_attr

A hash of attributes to use for the label tag

:default

returns tag without wrapping

:div

wraps tag in div tag

:fieldset

wraps tags in a fieldset, mostly useful for accessible checkboxset and radioset inputs

:fieldset_ol

same as :li, but also sets inputs_wrapper to :fieldset_ol

:li

wraps tag in li tag

:ol

same as :li, but also sets inputs_wrapper to :ol

:p

wraps tag in p tag

:span

wraps tag in span tag

:table

same as :trtd, but also sets inputs_wrapper to :table

:td

wraps tag in a td tag

:tr

same as :td, but also sets inputs_wrapper to :tr

:trtd

wraps tag in a tr tag with a td for the label and a td for the tag, useful for lining up inputs with the :explicit labeler without CSS

All of these except for :default respect the following options:

:wrapper_attr

A hash of attributes to use for the wrapping tag.

:default

uses a fieldset to wrap inputs

:div

uses a div tag to wrap inputs

:fieldset_ol

use both a fieldset and an ol tag to wrap inputs

:ol

uses an ol tag to wrap inputs, useful with :li wrapper

:table

uses a table tag to wrap inputs, useful with :trtd wrapper

:tr

uses a tr tag to wrap inputs, useful with :td wrapper

All of these support the following options:

:attr

A hash of attributes to use for the wrapping tag.

The :default, :fieldset_ol, and :table inputs_wrappers support the following options:

:legend

A text description for the inputs, using the legend tag for fieldsets and the caption tag for a table.

:legend_attr

A hash of attributes for the legend/caption tag.

The :table inputs_wrapper also supports the following options:

:labels

An array of labels, used to setup a row of table headers with the labels.

You can associate a group of transformers into a configuration. This allows you to specify a single :config option when creating a Form and have it automatically set all the related transformers.

There are a few configurations supported by default:

:default

All default transformers

:formtastic

fieldset_ol inputs_wrapper, li wrapper, explicit labeler

You can register and use your own configurations easily:

Forme.register_config(:mine, :wrapper=>:li, :inputs_wrapper=>:ol, :serializer=>:html_usa)
Forme::Form.new(:config=>:mine)

If you want to, you can base your configuration on an existing configuration:

Forme.register_config(:yours, :base=>:mine, :inputs_wrapper=>:fieldset_ol)

You can mark a configuration as the default using:

Forme.default_config = :mine

Forme ships with support for Bootstrap 5 HTML formatting. This support is shipped in it’s own file, so if you don’t use it, you don’t pay the memory penalty for loading it.

require 'forme/bs5'
Forme.default_config = :bs5

There is also support for Bootstrap versions 3-4:

require 'forme/bs3'
Forme.default_config = :bs3

All of these have external dependencies:

1. Rails built-in helpers

2. Formtastic

3. simple_form

4. padrino-helpers

Forme’s API draws a lot of inspiration from both Formtastic and simple_form.

MIT

Jeremy Evans <code@jeremyevans.net>