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Load Model

A glorified before_filter that loads an instance of an ActiveRecord object as the result of searching for said object against a model defined by a given model name. The value of the HTTP request parameter :id will be used as the default lookup value. LoadModel will give you the ability to require an instance be found and/or override several other default behaviors.

class SillyFellowController < Application
  load_model :silly_fellow
  def action

You can require that a model instance be found for all actions or given actions. Default behavior is to not require that a model instance be found. When require is on and a record is not found, a ThumbleMonks::RequiredRecordNotFound Exception is thrown; which extends from ActiveRecord::RecordNotFound, for your convenience.

To turn require on for all actions, simply pass true to a provided :require attribute, like so:

load_model :silly_fellow, :require => true

To turn require on for specific actions, pass an array of action names to :require. The model will be loaded for all actions, regardless of whether or not required is provided, but the exception will only be raised when an record is not found for the provided actions.

load_model :silly_fellow, :require => [:show, :update]

To use a different parameter key and model than the default, you can provide the values in the :paramater_key and :class options (though not necessary to provide them together), like the following:

load_model :foo, :class => :user, :parameter_key => :bar_id

In the above example, load_model will assume the parameter_key and the model's primary/foreign key are both the same. For instance, the above example would result in a call like the following:

@foo = User.find_by_bar_id(params[:bar_id])

If you want to use a different lookup/foreign key than the default, you can also provide that key name using the :foreign_key parameter; like so:

load_model :foo, :class => :user, :parameter_key => :bar_id,
  :foreign_key => :baz_id

Which would result in a call similar to the following:

@foo = User.find_by_baz_id(params[:bar_id])

If you want to only use load_model for some actions, you can still name them as you would with a before_filter using :only or :except. If you provide an :only and an :except value. :only will always win out over :except when there are collisions (i.e. you provide both in the same call)

load_model :foo, :only => [:show]
load_model :bar, :except => [:create]


Load Model supports a :through option. With :through, you can load a model via the association of an existing loaded model. This is especially useful for RESTful controllers.

load_model :user, :require => true, :parameter_key => :user_id
load_model :post, :through => :user

In this example, a @post record will be loaded through the @user record with essentially the following code:


All of the previously mentioned options still apply (:parameter_key, :foreign_key, :require, :only, and :except) except for the :class option. Meaning you could really mess around!

load_model :user, :require => true, :parameter_key => :user_id
load_model :post, :through => :person, :parameter_key => :foo_id, 
  :foreign_key => :baz_id

Would result in a call similar to the following:


Require works as you would expect.

If you would like load_model to not assume a pluralized association name, you can provide the association name with the :association option. Like so:

class Person < ActiveRecord::Base
  has_many :blog_postings

class PostController < ActionController::Base
  load_model :post, :through => :person, :assocation => :blog_postings


Perhaps you don't need to do a subquery on a model's association and you just need to load a model from another's belongs_to or has_one association. This would be impossible in the above example. Instead, will want to use the :from option. Like so:

class Post < ActiveRecord::Base
  belongs_to :user

class PostController < ActionController::Base
  load_model :post
  load_model :user, :from => :post

The example is contrived, but you get the point. Essentially, this would do the same as writing the following code:

@post = Post.find_by_id(params[:id])
@user = @post.user


sudo gem install thumblemonks-load_model


  1. Ruby 1.8.6 or higher
  2. Rails 2.x or higher


Anyone who developed, discussed, or any other way participated in HTTP, REST, and Rails.


Justin Knowlden