A minimal, object-oriented solution to generate Rails administrative index views. Through query objects and presenters, it features a customizable table generator and search forms with filtering/sorting.

The Rails ecosystem has many full-fledged solutions to generate administrative interfaces.

Although these tools are very handy to bootstrap a project quickly, they all obey the 80%-20% rule and tend to be very invasive, often mixing up different concerns on a single responsibility level, thus making tests unbelievably difficult to setup and write.

A time comes when these all-encompassing tools get in the way. And that will be the moment where all the cumulated saved time will be wasted to solve a single, trivial problem with ugly workarounds and epic facepalms.

So yes, if you're starting a small, short-lived project, go ahead with them, it will be fine! If you're building something that's more valuable or is meant to last longer, there are better alternatives.

The great thing is that you don't need to write a lot of code to get a more maintainable and modular administrative area. Gems like Inherited Resources and Simple Form, combined with Rails 3.1+ template-inheritance already give you ~90% of the time-saving features and the same super-DRY, declarative code that administrative interfaces offer, but with a far more relaxed contract.

If a particular controller or view needs something different from the standard CRUD/REST treatment, you can just avoid using those gems in that specific context, and fall back to standard Rails code. No workarounds, no facepalms. It seems easy, right? It is.

So what about Admino? Well, it complements the above-mentioned gems, giving you the the missing ~10%: a fast way to generate administrative index views.

To better illustrate how to create a 100%-custom, super-DRY administrative interface using Admino and the aforementioned gems, we prepared a repo with a sample Rails project you can take a look. The app is browsable at http://admino-example.herokuapp.com, and features a Bootstrap 3 theme.

Add this line to your application's Gemfile:

gem 'admino'

And then execute:

$ bundle

Admino::Query::Base implements the Query object pattern, that is, an object responsible for returning a result set (ie. an ActiveRecord::Relation) based on business rules.

Given a Task model, we can generate a TasksQuery query object subclassing Admino::Query::Base:

class TasksQuery < Admino::Query::Base
end

Each query object gets initialized with a hash of params, and features a #scope method that returns the filtered/sorted result set. As you may have guessed, query objects can be great companions to index actions:

class TasksController < ApplicationController
  def index
    @query = TasksQuery.new(params)
    @tasks = @query.scope
  end
end

You can specify how a TaskQuery must build a result set through a simple DSL.

The starting_scope method is in charge of defining the scope that will start the filtering/ordering chain:

class TasksQuery < Admino::Query::Base
  starting_scope { Task.all }
end

Task.create(title: 'Low priority task')

TaskQuery.new.scope.count # => 1

Once you define the following field:

class TasksQuery < Admino::Query::Base
  # ...
  search_field :title_matches
end

The #scope method will check the presence of the params[:query][:title_matches] key. If it finds it, it will augment the query with a named scope called :title_matches, expected to be found within the Task model. The scope needs to accept an argument.

class Task < ActiveRecord::Base
  scope :title_matches, ->(text) {
    where('title ILIKE ?', "%#{text}%")
  }
end

Task.create(title: 'Low priority task')
Task.create(title: 'Fix me ASAP!!1!')

TaskQuery.new.scope.count # => 2
TaskQuery.new(query: { title_matches: 'ASAP' }).scope.count # => 1

You can provide a default value with the default option:

class TasksQuery < Admino::Query::Base
  # ...
  search_field :title_matches, default: 'TODO'
end

class Task < ActiveRecord::Base
  enum :status, [:pending, :completed, :archived]
  scope :title_matches, ->(text) {
    where('title ILIKE ?', "%#{text}%")
  }
end

class TasksQuery < Admino::Query::Base
  # ...
  filter_by :status, [:completed, :pending]
  filter_by :deleted, [:with_deleted]
  filter_by :status, Task.statuses.keys
end

Just like a search field, with a declared filter group the #scope method will check the presence of a params[:query][:status] key. If it finds it (and its value corresponds to one of the declared scopes) it will augment the query with the scope itself:

class Task < ActiveRecord::Base
  scope :completed, -> { where(completed: true) }
  scope :pending,   -> { where(completed: false) }
end

Task.create(title: 'First task', completed: true)
Task.create(title: 'Second task', completed: true)
Task.create(title: 'Third task', completed: false)

TaskQuery.new.scope.count # => 3
TaskQuery.new(query: { status: 'completed' }).scope.count # => 2
TaskQuery.new(query: { status: 'pending' }).scope.count # => 1
TaskQuery.new(query: { status: 'foobar' }).scope.count # => 3

You can include a "reset" scope with the include_empty_scope option, and provide a default scope with the default option:

class TasksQuery < Admino::Query::Base
  # ...
  filter_by :time, [:last_month, :last_week],
            include_empty_scope: true,
            default: :last_week
end

class TasksQuery < Admino::Query::Base
  # ...
  sorting :by_due_date, :by_title
end

Once you declare some sorting scopes, the query object looks for a params[:sorting] key. If it exists (and corresponds to one of the declared scopes), it will augment the query with the scope itself. The model named scope will be called passing an argument that represents the direction of sorting (:asc or :desc).

The direction passed to the scope will depend on the value of params[:sort_order], and will default to :asc:

class Task < ActiveRecord::Base
  scope :by_due_date, ->(direction) { order(due_date: direction) }
  scope :by_title, ->(direction) { order(title: direction) }
end

expired_task = Task.create(due_date: 1.year.ago)
future_task = Task.create(due_date: 1.week.since)

TaskQuery.new(sorting: 'by_due_date', sort_order: 'desc').scope # => [ future_task, expired_task ]
TaskQuery.new(sorting: 'by_due_date', sort_order: 'asc').scope  # => [ expired_task, future_task ]
TaskQuery.new(sorting: 'by_due_date').scope                     # => [ expired_task, future_task ]

It's very common ie. to paginate a result set. The block declared in the ending_scope block will be always appended to the end of the chain:

class TasksQuery < Admino::Query::Base
  ending_scope { |q| page(q.params[:page]) }
end

If you do not want to pollute your ActiveRecord model with all these scopes, you are free to implement them on the query object itself (just make sure to suffix them with _scope):

class Task < ActiveRecord::Base
end

class TasksQuery < Admino::Query::Base
  search_field :title_matches

  def title_matches_scope(scope, text)
    scope.where('title ILIKE ?', "%#{text}%")
  end
end

A query object supports various methods to inspect the available search fields, filters and sortings, and their state:

query = TaskQuery.new
query.search_fields  # => [ #<Admino::Query::SearchField>, ... ]
query.filter_groups  # => [ #<Admino::Query::FilterGroup>, ... ]

search_field = query.search_field_by_name(:title_matches)

search_field.name      # => :title_matches
search_field.present?  # => true
search_field.value     # => 'ASAP'

filter_group = query.filter_group_by_name(:status)

filter_group.name                        # => :status
filter_group.scopes                      # => [ :completed, :pending ]
filter_group.active_scope                # => :completed
filter_group.is_scope_active?(:pending)  # => false

sorting = query.sorting                  # => #<Admino::Query::Sorting>
sorting.scopes                           # => [ :by_title, :by_due_date ]
sorting.active_scope                     # => :by_due_date
sorting.is_scope_active?(:by_title)      # => false
sorting.ascending?                       # => true

Admino offers some helpers that make it really easy to generate search forms and filtering links:

<%# generate the search form %>
<%= search_form_for(query) do |q| %>
  <%# generate inputs from search_fields %>
  <p>
    <%= q.label :title_matches %>
    <%= q.text_field :title_matches %>
  </p>
  <p>
    <%= q.submit %>
  </p>
  
  <%# generate inputs from filter_by %>
  <p>
	<%= q.label :status %>
	<%= q.select :status, Task.statuses.keys %>  
  </p>

  <%# if filter_by has only one scope you can use a checkbox %>  
  <p>
    <%= q.check_box :deleted, {}, checked_value: "with_deleted" %>
    <%= q.label :deleted %>
  </p>
<% end %>

<%# generate the filtering links %>
<% filters_for(query) do |filter_group| %>
  <h6><%= filter_group.name %></h6>
  <ul>
    <% filter_group.each_scope do |scope| %>
      <li><%= scope.link %><li>
    <% end %>
  </ul>
<% end %>

<%# generate the sorting links %>
<h6>Sort by</h6>
<ul>
  <% sortings_for(query) do |scope| %>
    <li><%= scope.link %></li>
  <% end %>
</ul>

The great thing is that:

• the search form gets automatically filled in with the last input the user submitted
• a is-active CSS class gets added to the currently active filter scopes
• if a particular filter link has been clicked and is now active, it is possible to deactivate it by clicking on the link again
• a is-asc/is-desc CSS class gets added to the currently active sorting scope
• if a particular sorting scope link has been clicked and is now in ascending order, it is possible to make it descending by clicking on the link again

If you prefer using Simple Form, please use the simple_search_form_for helper instead.

The #link methods are very flexible, allowing you to change almost every aspect of the generated links:

<% filter_group.each_scope do |scope| %>
  <li><%= scope.link 'Custom title',
                     active_class: 'active',
                     class: 'custom-class'
  %><li>
<% end %>

Please refer to the tests for the details.

Suppose you have to filter the tasks based on the @current_user work group. You can easily provide an alternative starting scope from the controller passing it as an argument to the #scope method:

def index
  @query = TasksQuery.new(params)
  @project_tasks = @query.scope(@current_user.team.tasks)
end

Suppose the presence of a model scope that requires a non-textual argument (ie. a date):

class Task < ActiveRecord::Base
  scope :due_date_from, ->(date) { where('due_date >= ?', date) }
end

Admino can perform some automatic coertions to the textual parameter it gets, and pass the coerced value to the scope:

class TasksQuery < Admino::Query::Base
  search_field :due_date_from, coerce: :to_date
end

query = TaskQuery.new(query: { due_date_from: '2014-03-01' })
query.search_field_by_name(:due_date_from).value # => #<Date Sat, 01 Mar 2014>

If a specific coercion cannot be performed with the provided input, the scope won't be chained. The following coertions are available:

• :to_boolean
• :to_constant
• :to_date
• :to_datetime
• :to_decimal
• :to_float
• :to_integer
• :to_symbol
• :to_time

Please see the Coercible::Coercer::String class for details.

If you need to setup a default sorting, you can pass some optional arguments to the sorting declaration:

class TasksQuery < Admino::Query::Base
  # ...
  sorting :by_due_date, :by_title,
          default_scope: :by_due_date,
          default_direction: :desc
end

To localize the search form labels, as well as the group filter names and scope links, please refer to the following YAML file:

en:
  query:
    attributes:
      tasks_query:
        title_matches: 'Title contains'
    filter_groups:
      tasks_query:
        status:
          name: 'Filter by status'
          scopes:
            completed: 'Completed'
            pending: 'Pending'
    sorting_scopes:
      task_query:
        by_due_date: 'By due date'
        by_title: 'By title'

Admino offers a table_for helper that makes it really easy to generate HTML tables from a set of records:

<%= table_for(@tasks, class: Task) do |row, record| %>
  <%= row.column :title %>
  <%= row.column :completed do %>
    <%= record.completed ? '✓' : '✗' %>
  <% end %>
  <%= row.column :due_date %>
<% end %>

With produces the following output:

<table>
  <thead>
    <tr>
      <th role='title'>Title</th>
      <th role='completed'>Completed</th>
      <th role='due-date'>Due date</th>
    </tr>
  <thead>
  <tbody>
    <tr class='is-even'>
      <td role='title'>Call mum ASAP</td>
      <td role='completed'>✓</td>
      <td role='due-date'>2013-02-04</td>
    </tr>
    <tr class='is-odd'>
      <!-- ... -->
    </tr>
  <tbody>
</table>

Often tables need to offer some kind of action associated with the records. The table builder implements the following DSL to support that:

<%= table_for(@tasks, class: Task) do |row, record| %>
  <%# ... %>
  <%= row.actions do %>
    <%= row.action :show, admin_task_path(record) %>
    <%= row.action :edit, edit_admin_task_path(record) %>
    <%= row.action :destroy, admin_task_path(record), method: :delete %>
  <% end %>
<% end %>

<table>
  <thead>
    <tr>
      <!-- ... -->
      <th role='actions'>Actions</th>
    </tr>
  <thead>
  <tbody>
    <tr class='is-even'>
      <!-- ... -->
      <td role='actions'>
        <a href='/admin/tasks/1' role='show'>Show</a>
        <a href='/admin/tasks/1/edit' role='edit'>Edit</a>
        <a href='/admin/tasks/1' role='destroy' data-method='delete'>Destroy</a>
      </td>
    </tr>
  <tbody>
</table>

If you want to make the table headers sortable, then please create an Admino query object class to define the available sorting scopes.

class TaskQuery < Admino::Query::Base
  sorting :by_title, :by_due_date
end

You can then pass the query object as a parameter to the table presenter initializer, and associate table columns to specific sorting scopes of the query object using the sorting directive:

<% query = present(@query) %>

<%= table_for(@tasks, class: Task) do |row, record| %>
  <%= row.column :title, sorting: :by_title %>
  <%= row.column :due_date, sorting: :by_due_date %>
<% end %>

This generates links that allow the visitor to sort the result set in ascending and descending direction:

<table>
  <thead>
    <tr>
      <th role='title'>
        <a href='/admin/tasks?sorting=by_title&sort_order=desc' class='is-asc'>Title</a>
      </th>
      <th role='due-date'>
        <a href='/admin/tasks?sorting=by_due_date&sort_order=asc'>Due date</a>
      </th>
    </tr>
  <thead>
  <!-- ... -->
</table>

The #column and #action methods are very flexible, allowing you to change almost every aspect of the generated table cells:

<%= table_for(@tasks, class: Task, html: { class: 'table-class' }) do |row, record| %>
  <%= row.column :title, 'Custom title',
                 class: 'custom-class', role: 'custom-role', data: { custom: 'true' },
                 sorting: :by_title, sorting_html_options: { desc_class: 'down' }
  %>
  <%= row.action :show, admin_task_path(record), 'Custom label',
                 class: 'custom-class', role: 'custom-role', data: { custom: 'true' }
  %>
<% end %>

If you need more power, you can also subclass Admino::Table::Presenter. For each HTML element, there's a set of methods you can override to customize it's appeareance. Table cells are generated through two collaborator classes: Admino::Table::HeadRow and Admino::Table::ResourceRow. You can easily replace them with a subclass if you want. To grasp the idea here's an example:

class CustomTablePresenter < Admino::Table::Presenter
  private

  def table_html_options
    { class: 'table-class' }
  end

  def tbody_tr_html_options(resource, index)
    { class: 'tr-class' }
  end

  def zebra_css_classes
    %w(one two three)
  end

  def resource_row(resource, view_context)
    ResourceRow.new(resource, view_context)
  end

  def head_row(collection_klass, query, view_context)
    HeadRow.new(collection_klass, query, view_context)
  end

  class ResourceRow < Admino::Table::ResourceRow
    private

    def action_html_options(action_name)
      { class: 'action-class' }
    end

    def show_action_html_options
      { class: 'show-action-class' }
    end

    def column_html_options(attribute_name)
      { class: 'column-class' }
    end
  end

  class HeadRow < Admino::Table::ResourceRow
    def column_html_options(attribute_name)
      { class: 'column-class' }
    end
  end
end

<%= table_for(@tasks, class: Task, presenter: CustomTablePresenter) do |row, record| %>
  <%= row.column :title, 'Custom title',
                 class: 'custom-class', role: 'custom-role', data: { custom: 'true' },
                 sorting: :by_title, sorting_html_options: { desc_class: 'down' }
  %>
  <%= row.action :show, admin_task_path(record), 'Custom label',
                 class: 'custom-class', role: 'custom-role', data: { custom: 'true' }
  %>
<% end %>

Please refer to the tests for all the details.

If your controller actions are generated through Inherited Resources, then you can always get the URL pointing to the show action with the resource_path helper method. Similar helpers are available for the other REST actions too (new, edit, destroy).

More in general, if you are able to programmatically generate/obtain the URLs of your row actions, you can subclass Admino::Table::Presenter and declare them:

class CustomTablePresenter < Admino::Table::Presenter
  private

  def resource_row(resource, view_context)
    ResourceRow.new(resource, view_context)
  end

  class ResourceRow < Admino::Table::ResourceRow
    def show_action_url
      h.resource_url(resource)
    end

    def edit_action_url
      h.edit_resource_url(resource)
    end

    def destroy_action_url
      h.resource_url(resource)
    end

    def destroy_action_html_options
      { method: :delete }
    end
  end
end

This will enable you to generate row actions even faster, simply declaring them as arguments to the #actions DSL method:

<%= table_for(@tasks, class: Task, presenter: CustomTablePresenter) do |row, record| %>
  <%# ... %>
  <%= row.actions :show, :edit, :destroy %>
<% end %>

As funny it may sound, it is strongly suggested to pass to the table presenter an array of records which in turn have been already presented. This enables you to use as columns not only the raw attributes of the model, but all the methods defined in the presenter.

Furthermore, if the record presenter includes the Showcase::Traits::Record trait, each row of the table will automatically have an unique id attribute thanks to the #dom_id method.

class TaskPresenter < Showcase::Presenter
  include Showcase::Traits::Record

  def truncated_title
    h.truncate(title, length: 50)
  end
end

<% tasks = present_collection(@tasks)

<%= Admino::Table::Presenter.new(tasks, Task, self).to_html do |row, record| %>
  <%= row.column :truncated_title, 'Title' %>
<% end %>

<table>
  <thead>
    <th role='truncated-title'>Title</th>
  <thead>
  <tbody>
    <tr id='task_1' class='is-even'>
      <td role='truncated-title'>Call mum ASAP</td>
    </tr>
    <tr id='task_2' class='is-odd'>
      <td role='truncated-title'>Buy some milk</td>
    </tr>
  <tbody>
</table>

Column titles are generated using the model #human_attribute_name method, so if you already translated the model attribute names, you're good to go. To translate actions, please refer to the following YAML file:

en:
  activerecord:
    attributes:
      task:
        title: 'Title'
        due_date: 'Due date'
        completed: 'Completed?'
  table:
    actions:
      task:
        title: 'Actions'
        show: 'Details'
        edit: 'Edit task'
        destroy: 'Delete'

Install gems:

$ bundle
$ bundle exec appraisal

Launch tests:

bundle exec appraisal rake