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copied!<p><strong>attr_accessor</strong> and <strong>attr_accessible</strong>, despite almost identical spelling, are absolutely different methods.</p> <p><strong>attr_accessor</strong>, a native Ruby method which defines a getter and a setter method for the instance of the class:</p> <pre><code>class User attr_accessor :password end u = User.new u.password = "secret" u.password # => "secret" </code></pre> <p><strong>attr_accessible</strong> is a method brought by Rails and it is meant to "whitelist" <em>already existing</em> attributes of a model. Attributes enumerated in <strong>attr_accessible</strong> can be later changed via mass-assignment of model attributes (while other attributes will be blacklisted and not changeable):</p> <pre><code>class Account < ActiveRecord::Base # First, you define 2 attributes: "password" and "created_at" attr_accessor :password attr_accessor :created_at # Now you say that you want "password" attribute # to be changeable via mass-assignment, while making # "created_at" to be non-changeable via mass-assignment attr_accessible :password end a = Account.new # Perform mass-assignment (which is usually done when you update # your model using the attributes submitted via a web form) a.update_attributes(:password => "secret", :created_at => Time.now) a.password # => "secret" # "password" is changed a.created_at # => nil # "created_at" remains not changed </code></pre> <p>You use <strong>attr_accessible</strong> to prevent meddling with some attributes of your models by "outsiders" (e.g. you wouldn't want your "Account.superadmin" attribute to be changeable via a simple form submission, which would be a bad security issue).</p> <p>Note, that you can change the attributes individually, regardless of their "whitelisting/blacklisting" status:</p> <pre><code>a.created_at = Time.now a.created_at # => 2012-09-16 10:03:14 </code></pre>

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