Monkey patching ActiveAdmin

app-slash-admin-slash-active_admin_extensions.rb

# This file extends and overrides parts of the ActiveAdmin DSL and internals
# in order to provide support for automatically displaying and editing images,
# which in our infrastructure are stored as URLs whose column names end in "img".
# Since this file will be reloaded frequently in the development environment,
# all operations done at load time (class_eval's, etc.) MUST be idempotent.

ActiveAdmin::Views::TableFor.class_eval do

  def img_column(col_sym=:img, title="Image")
    column title, sortable: false do |obj|
      url = obj.send(col_sym)
      link_to(filepicker_image_tag(url, width: 100, height: 100), url)
    end
  end

end

# You can also subclass this and do `index as: MyIndexAsTableSubclass` to get the same functionality
ActiveAdmin::Views::IndexAsTable.class_eval do
  def default_table
    proc do
      selectable_column
      id_column
      resource_class.content_columns.each do |col|
        if col.name.ends_with? "img"
          img_column col.name.to_sym
        else
          column col.name.to_sym
        end
      end
      default_actions
    end
  end
end

ActiveAdmin::Views::AttributesTable.class_eval do
  def content_for(record, attr)
    previous = current_arbre_element.to_s

    if attr.to_s.ends_with? "img"
      value = find_attr_value(record, attr)
      value = link_to(filepicker_image_tag(value, width: 200, height: 200), value)
    else
      value = pretty_format find_attr_value(record, attr)
    end

    value.blank? && previous == current_arbre_element.to_s ? empty_value : value
  end
end

class FilepickerForActiveAdminInput
  include Formtastic::Inputs::Base
  def to_html
    input_wrapping do
      label_html << 
      builder.filepicker_field(method, input_html_options)
    end
  end
end

ActiveAdmin::FormBuilder.class_eval do

  protected

  def default_input_type(method, options = {})
    if column = column_for(method) and column.type == :string
      if method.to_s.ends_with? "img"
        return :filepicker_for_active_admin
      end
    end
    super
  end

end

config-slash-initializers-slash-inflections.rb

# This will provide human-readable column names across the board, including all the
# ActiveAdmin pages (which all use pretty_format which uses the Inflector).

ActiveSupport::Inflector.inflections do |inflect|
  inflect.human /img$/, '\1image'
end