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A simple and Rubyish view helper for Rails 3, Rails 4, Rails 5, and Rails 6. Keep your helpers and views Object-Oriented!


  1. automatically mixes decorator module into corresponding model only when:
    1. passing a model or collection of models or an instance of ActiveRecord::Relation from controllers to views
    2. rendering partials with models (using :collection or :object or :locals explicitly or implicitly)
    3. fetching already decorated Active Record model object's association
  2. the decorator module runs in the model's context. So, you can directly call any attributes or methods in the decorator module
  3. since decorators are considered as sort of helpers, you can also call any ActionView's helper methods such as content_tag or link_to

Supported versions

  • Ruby 2.0.0, 2.1.x, 2.2.x, 2.3.x, 2.4.x, 2.5.x, 2.6.x, and 2.7 (trunk)

  • Rails 3.2.x, 4.0.x, 4.1.x, 4.2.x, 5.0, 5.1, 5.2, and 6.0 (edge)

Supported ORMs

ActiveRecord, ActiveResource, and any kind of ORMs that uses Ruby Objects as model objects


  1. bundle 'active_decorator' gem
  2. create a decorator module for each AR model. For example, a decorator for a model User should be named UserDecorator. You can use the generator for doing this ( % rails g decorator user )
  3. Then it's all done. Without altering any single line of the existing code, the decorator modules will be automatically mixed into your models only in the view context.


Auto-decorating via render

  • Model ```ruby class Author < ActiveRecord::Base

    first_name:string last_name:string

    end ```

  • Controller ruby class AuthorsController < ApplicationController def show(id) # powered by action_args @author = Author.find id end end

  • Decorator ruby module AuthorDecorator def full_name "#{first_name} #{last_name}" end end

  • View ```erb <%# @author here is auto-decorated in between the controller and the view %>

<%= @author.full_name %>

### Auto-decorating via AR model's associated objects ###

* Models

class Author < ActiveRecord::Base # name:string has_many :books end

class Book < ActiveRecord::Base # title:string url:string belongs_to :author end ```

  • Controller ruby class AuthorsController < ApplicationController def show(id) @author = Author.find id end end

  • Decorator ruby module BookDecorator def link link_to title, url end end

  • View ```erb

<%= %>

    <% @author.books.each do |book| %> <%# `book` here is auto-decorated because @author is a decorated instance %>
  • <%= %>
  • <% end %>

### Using ActiveDecorator outside of Action View ###

Sometimes you may want to use decorators outside of Action View, for example,
for background tasks for ActiveJob.
For such use case, ActiveDecorator module provides `run_with` method
that takes some kind of Action View and a block.

ActiveDecorator::ViewContext.run_with do ## perform some heavy jobs here end ```


You can test a decorator using your favorite test framework by decorating the model instance with


Considering an Organization model and its simple decorator:

module OrganizationDecorator
  def full_name
    "#{first_name} #{last_name}"

An RSpec test would look like:

describe '#full_name' do
  it 'returns the full organization name' do
    organization = 'John', last_name: 'Doe')
    decorated_organization = ActiveDecorator::Decorator.instance.decorate(organization)

    expect(decorated_organization.full_name).to eq('John Doe')

Configuring the decorator suffix

By default, ActiveDecorator searches a decorator module named + "Decorator"

If you would like a different rule, you can configure in your initializer.

ActiveDecorator.configure do |config|
  config.decorator_suffix = 'Presenter'

Contributing to ActiveDecorator

  • Fork, fix, then send me a pull request.


Copyright (c) 2011 Akira Matsuda. See MIT-LICENSE for further details.