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 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 resource do |f|
  inputs :title, :body
  actions
end

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

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

  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 do
      f.has_many :categories, heading: 'Themes', allow_destroy: true, new_record: false do |a|
        a.input :title
      end
    end
    f.inputs do
      f.has_many :taggings, sortable: :position do |t|
        t.input :tag
      end
    end
    f.inputs do
      f.has_many :comment, new_record: 'Leave Comment' do |b|
        b.input :body
      end
    end
    f.actions
  end

end

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.

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 :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.

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

Displaying Errors

To display a list of all validation errors:

form do |f|
  f.semantic_errors *f.object.errors.keys
  # ...
end

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

Tabs

You can arrage content in tabs as shown below:

  form do |f|
    tabs do
      tab 'Basic' do
        f.inputs 'Basic Details' do
          f.input :email
          f.input :password
          f.input :password_confirmation
        end
      end

      tab 'Advanced' do
        f.inputs 'Advanced Details' do
          f.input :role
        end
      end
    end
    f.actions
  end