ActivePresenter is the presenter library you already know! (…if you know ActiveRecord)

By acting nearly identically to ActiveRecord models, ActivePresenter makes presenters highly approachable to anybody who is already familiar with ActiveRecord.

As a gem:

$ sudo gem install active_presenter

As a rails gem dependency:

config.gem 'active_presenter'

Or get the source from github:

$ git clone git://github.com/giraffesoft/active_presenter.git

(or fork it at github.com/giraffesoft/active_presenter)

Creating a presenter is as simple as subclassing ActivePresenter::Base. Use the presents method to indicate which models the presenter should present.

class SignupPresenter < ActivePresenter::Base
  presents :user, :account
end

In the above example, :user will (predictably) become User. If you want to override this behavior, specify the desired types in a hash, as so:

class PresenterWithTwoAddresses < ActivePresenter::Base
  presents :primary_address => Address, :secondary_address => Address
end

Then, you can instantiate the presenter using either, or both of two forms.

For example, if you had a SignupPresenter that presented User, and Account, you could specify arguments in the following two forms:

1. SignupPresenter.new(:user_login => 'james', :user_password => 'swordfish', :user_password_confirmation => 'swordfish', :account_subdomain => 'giraffesoft')

  - This form is useful for initializing a new presenter from the params hash: i.e. SignupPresenter.new(params[:signup_presenter])

2. SignupPresenter.new(:user => User.find(1), :account => Account.find(2))

  - This form is useful if you have instances that you'd like to edit using the presenter. You can subsequently call presenter.update_attributes(params[:signup_presenter]) just like with a regular AR instance.

Both forms can also be mixed together: SignupPresenter.new(:user => User.find(1), :user_login => ‘james’).

In this case, the login attribute will be updated on the user instance provided.

If you don’t specify an instance, one will be created by calling Model.new

The #valid? method will return true or false based on the validity of the presented objects.

This is calculated by calling #valid? on them.

You can retrieve the errors in two ways.

1. By calling #errors on the presenter, which returns an instance of ActiveRecord::Errors where all the attributes are in type_name_attribute_name form (i.e. You'd retrieve an error on User#login, by calling @presenter.errors.on(:user_login)).

2. By calling @presenter.user_errors, or @presenter.user.errors to retrieve the errors from one presentable.

Both of these methods are compatible with error_messages_for. It just depends whether you’d like to show all the errors in one block, or whether you’d prefer to break them up.

ActivePresenter supports attr_protected and attr_accessible just like an ActiveRecord object to avoid mass assignment. This can be leveraged to provide an additional layer of protection at the presenter level.

class AccountPresenter < ActivePresenter::Base
  presents :user, :profile
  attr_accessible :user_email, :profile_birthday
end

You can save your presenter the same way you’d save an ActiveRecord object. Both #save, and #save! behave the same way they do on a normal AR model.

Callbacks work exactly like ActiveRecord callbacks. before_save, and after_save are available.

Note that if any of your after_save callbacks return false, the rest of them will not be run. This is consistent with AR behavior.

ActivePresenter was created, and is maintained by Daniel Haran and James Golick on the train ride to RubyFringe from Montreal.

ActivePresenter for Rails 3 is currently maintained by Josh Martin and Johnno Loggie

ActivePresenter is available under the MIT License