SimpleAdmin is a simple set of templates and controllers that can be used to quickly build out an admin section on your Rails site. It is heavily based on the popular ActiveAdmin gem from Greg Bell and VersaPay (in fact, the default stylesheets, javascripts, and images come directly from the ActiveAdmin project because they are awesome).

So why a new gem? ActiveAdmin has a lot of features and dependencies out of the box. These are great but are often more than you need, and unfortunately they create a lot of complexity in the underlying gem and integration. SimpleAdmin eschews much of that complexity and is instead a basic Rails engine. This makes debugging problems simpler as there are fewer dependencies, less meta-programming, and a smaller set of features.

In your Gemfile, include simple_admin and formtastic (and fastercsv if you are on an older version of Ruby):

gem "simple_admin"
gem "formtastic"
gem "fastercsv" # if Ruby < 1.9

Bundle install:

bundle

Generate out the configuration:

rails g simple_admin:install

Install the assets into your public folder so that they can be served by your web server instead of being served through rails.

rails g simple_admin:assets

Add any administration interfaces (for example, in app/admin/posts.rb):

SimpleAdmin.register :post do
end

Restart rails and check out your new admin interface.

Although you could use the simple registration pattern above, you may need some more control. Within the register block you can override the defaults using the following commands:

• before

• index

• show

• form

The before helper allows you to specify any before_filter style logic. It requires a block which is executed in the context of the controller prior to the page being displayed:

SimpleAdmin.register :post do
  before do
    # You could use this instead of the default config option
    require_admin
  end
end

You can also specify to which actions the before block should be applied:

SimpleAdmin.register :post do
  before :only => [:create, :destroy] do
    require_admin
  end
end

The index helper controls the index display. If you don’t include the index command then a default index page will be setup. If you do include it you can override the behavior. You can pass a title option to modify the default page title:

SimpleAdmin.register :post do
  # Customizing the title on the page
  index :title => 'Posts people have made'
end

The index helper also accepts a block. Within the block you have access modify the default filters and attributes. If you don’t include an attributes specification or a filters specification then the defaults will be used.

Within the index, show, and form blocks, the attributes command works the same. It accepts either except or only as an option to limit the list of default attributes:

SimpleAdmin.register :post do
  index do
    # Customize what attributes show using except
    attributes :except => [:id, :body]
  end
end

SimpleAdmin.register :post do
  index do
    # Customize what attributes show using only
    attributes :only => [:id, :title]
  end
end

You can omit these options and instead include a block. Within the block you can call

• clear

• defaults

• attribute

Clearing the list of attributes allows you complete control over what shows. The defaults helper is not used very often, but allows you to reset to the default list of attributes:

SimpleAdmin.register :post do
  index do
    attributes do
      # No attributes
      clear
      # An attribute
      attribute :title
      # Add an attribute with some data
      attribute :body, :title => "Post content" {|post| post.body.slice(60) }
    end
  end
end

The attribute command allows you to add a new attribute (if you had called clear) or override an already included default (if you had not called clear, or had already specified an attribute). The attribute helper expects the attribute name (as a symbol), any options, and an optional block which will be evaluated at the time of display. The only options that are expected are :title which controls the associated label or header and :sortable which is only used within the index (and which can only be set to false).

SimpleAdmin.register :post do
  index do
  end

  # The show section allows you to control the show page
  show do
    # Control which attributes are displayed
    attributes :only => [:title, :body]
  end

  # The form section allows you to control the new and edit pages
  form do
    # Control which attributes can be modified
    attributes do
      clear
      attribute :title
      attribute :body
    end
  end
end

Within the index you can also specify filters, which work exactly like attributes except that they control the search and filtering form on the right. You can also customize the filter by passing :as and :collection options.

SimpleAdmin.register :post do
  index do
    attributes do
      # This is not necessary, attributes are defaulted automatically
      defaults
    end

    filters do
      # No filters
      clear
      # Add a filter for searching the title
      filter :title
    end
  end
end

Finally, within index, show and form you can specify any number of sidebar helpers. Sidebars require a block which is executed at the time of rendering:

SimpleAdmin.register :post do
  index do
    sidebar do
      # Within index you have @collection, in other views you have @resource
      your_post_stats_helper(@collection)
    end
  end
end

When you generate simple_admin into your application a new mount point is automatically created:

mount SimpleAdmin::Engine => '/admin'

You can change this path however you see fit.

The available actions for each admin interface can also be customized:

SimpleAdmin.register :posts, :actions => [:index, :show] do
end

These will be directly reflected in the routes for the interface. If changed, you will need to restart your Rails server as the routes are generated at initialization. Available actions are:

• index

• new

• show

• edit

• destroy

• create

• update

You can also see the routes that are generated by your admin interfaces by running:

rake routes:simple_admin

All of the configuration for SimpleAdmin happens within the config/initializers/simple_admin.rb file that is generated when you run the generator.

The require_user_method setting allows you to specify which controller method should be called before rendering any admin pages. There is no default for this method. If it is not present then simple_admin will not do any admin verification prior to performing its controller actions.

It is possible to check for admin status using application level before filters or even using the before block within each individual admin interface registration.

To set this, specify the controller method you want called as a symbol:

config.require_user_method = :require_admin

The current_user_method is used by simple_admin to determine if there is a logged in user. There is no default for this property. If it is not present, no logged in user method will be checked and user information will not be displayed in the header of admin forms.

To set this, specify the controller method you want called as a symbol:

config.current_user_method = :current_user

The current_user_name_method is used by simple_admin to access the display name of the currently logged in user. There is no default for this property. If it is not present, any logged in user name will not be displayed in the header of admin forms.

To set this, specify the controller method you want called as a symbol:

config.current_user_name_method = :current_user_name

The site_title is displayed in the header of admin pages. If empty this value defaults to Rails.application.class.parent_name.titleize:

config.site_title = "My Website"

The default_per_page value allows you to control how many results appear on admin index pages. This value is fed into kaminari and is defaulted to 25 if not present:

config.default_per_page = 25

The form_for_helper defaults to the :semantic_form_for helper from formtastic. If you want to use another engine, like simple_form you can change this property and the gem requirements. Note that the default styling from active_admin relies on formtastic output.

config.form_for_helper = :semantic_form_for

The stylesheet and javascript properties are used within the admin layout and are defaulted to the active_admin styles and scripts. You may want to override these styles, or simply use the asset pipeline instead of installing them to your public folder. These properties allow you to manage where the assets are stored (either within the default pipeline or no). By default, SimpleAdmin assumes you have run the asset generator (rails g simple_admin:assets) and that these files live within your public folder:

config.stylesheet = "/stylesheets/simple_admin/active_admin.css"
config.javascript = "/javascripts/simple_admin/active_admin.js"

To run the specs you need to clone this repository, bundle, then generate the sample application:

rake sample

I went against the defaults from Rails 3.1 because one rake task is simpler, and this can target any rails version currently installed for testing. Plus, I use specs.

After that:

rake spec

• Jeff Rafter

• Your name here

Special thanks to the ActiveAdmin team and Greg Bell (@gregbell). I cribbed tons off ActiveAdmin, and used the default ActiveAdmin styles. This represents large portion of this gem.

Thanks also Nick Plante (@zapnap) for helping get the specs organized in the engine and for fighting through the refactoring with me.

Thanks also to Ryan Bigg (@ryanbigg) for his Forem project and help in IRC.