Forms

Active Admin gives you complete control over the output of the form by creating a thin DSL on top of Formtastic:

ActiveAdmin.register Post do

  form title: 'A custom title' do |f|
    inputs 'Details' do
      input :title
      input :published_at, label: "Publish Post At"
      li "Created at #{f.object.created_at}" unless f.object.new_record?
      input :category
    end
    panel 'Markup' do
      "The following can be used in the content below..."
    end
    inputs 'Content', :body
    para "Press cancel to return to the list without saving."
    actions
  end

end

For more details, please see Formtastic's documentation.

Default

Resources come with a default form defined as such:

form do |f|
  f.semantic_errors # shows errors on :base
  f.inputs          # builds an input field for every attribute
  f.actions         # adds the 'Submit' and 'Cancel' buttons
end

Partials

If you want to split a custom form into a separate partial use:

ActiveAdmin.register Post do
  form partial: 'form'
end

Which looks for something like this:

# app/views/admin/posts/_form.html.arb
active_admin_form_for [:admin, resource] do |f|
  inputs :title, :body
  actions
end

This is a regular Rails partial so any template engine may be used.

You can also use the ActiveAdmin::FormBuilder as builder in your Formtastic Form for use the same helpers are used in the admin file:

  = semantic_form_for [:admin, @post], builder: ActiveAdmin::FormBuilder do |f|
    = f.inputs "Details" do
      = f.input :title
    - f.has_many :taggings, sortable: :position, sortable_start: 1 do |t|
      - t.input :tag
    = f.actions

Nested Resources

You can create forms with nested models using the has_many method, even if your model uses has_one:

ActiveAdmin.register Post do
  permit_params :title,
                :published_at,
                :body,
                categories_attributes: [:id, :title, :_destroy],
                taggings_attributes: [:id, :tag],
                comment_attributes: [:id, :body, :_destroy]

  form do |f|
    f.inputs 'Details' do
      f.input :title
      f.input :published_at, label: 'Publish Post At'
    end
    f.inputs 'Content', :body
    f.inputs 'Themes' do
      f.has_many :categories, heading: false, allow_destroy: true, new_record: false do |a|
        a.input :title
      end
    end
    f.inputs 'Tags' do
      f.has_many :taggings, heading: false, sortable: :position, sortable_start: 1 do |t|
        t.input :tag
      end
    end
    f.inputs 'Comments' do
      f.has_many :comments,
                 heading: false,
                 new_record: 'Leave Comment',
                 remove_record: 'Remove Comment',
                 allow_destroy: -> (c) { c.author?(current_admin_user) } do |b|
        b.input :body
      end
    end
    f.actions
  end

end

NOTE: In addition to using has_many as illustrated above, you'll need to add accepts_nested_attributes to your parent model and configure strong parameters

The :allow_destroy option adds a checkbox to the end of the nested form allowing removal of the child object upon submission. Be sure to set allow_destroy: true on the association to use this option. It is possible to associate :allow_destroy with a string or a symbol, corresponding to the name of a child object's method that will get called, or with a Proc object. The Proc object receives the child object as a parameter and should return either true or false.

The :heading option adds a custom heading. You can hide it entirely by passing false.

The :new_record option controls the visibility of the new record button (shown by default). If you pass a string, it will be used as the text for the new record button.

The :remove_record option controls the text of the remove button (shown after the new record button is pressed). If you pass a string, it will be used as the text for the remove button.

The :sortable option adds a hidden field and will enable drag & drop sorting of the children. It expects the name of the column that will store the index of each child.

The :sortable_start option sets the value (0 by default) of the first position in the list.

Datepicker

ActiveAdmin offers the datepicker input, which uses the jQuery UI datepicker. The datepicker input accepts any of the options available to the standard jQueryUI Datepicker. For example:

form do |f|
  f.input :starts_at, as: :datepicker,
                      datepicker_options: {
                        min_date: "2013-10-8",
                        max_date: "+3D"
                      }

  f.input :ends_at, as: :datepicker,
                    datepicker_options: {
                      min_date: 3.days.ago.to_date,
                      max_date: "+1W +5D"
                    }
end

Datepicker also accepts the :label option as a string or proc to display. If it's a proc, it will be called each time the datepicker is rendered.

Displaying Errors

To display a list of all validation errors:

form do |f|
  f.semantic_errors *f.object.errors.attribute_names

  # ...
end

This is particularly useful to display errors on virtual or hidden attributes.

Customize the Create Another checkbox

In order to simplify creating multiple resources you may enable ActiveAdmin to show nice "Create Another" checkbox alongside of Create Model button. It may be enabled for the whole application:

ActiveAdmin.setup do |config|
  config.create_another = true
end

or for the particular resource:

ActiveAdmin.register Post do
  config.create_another = true
end