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copied!<p>No. <code>alias_method</code> is a standard method from Ruby. <code>alias_method_chain</code> is a Rails add-on designed to simplify the common action of aliasing the old method to a new name and then aliasing a new method to the original name. So, if for example you are creating a new version of the <code>method</code> method with the new feature <code>new_feature</code>, the following two code examples are equivalent:</p> <pre><code>alias_method :method_without_new_feature, :method alias_method :method, :method_with_new_feature </code></pre> <p>and</p> <pre><code>alias_method_chain :method, :new_feature </code></pre> <hr> <h2>EDIT</h2> <p>Here is a hypothetical example: suppose we had a Person class with a method <code>rename</code>. All it does is take a string like "John Doe", split on the space, and assign parts to first_name and last_name. For example:</p> <pre><code>person.rename("Steve Jones") person.first_name #=> Steve person.last_name #=> Jones </code></pre> <p>Now we're having a problem. We keep getting new names that aren't capitalized properly. So we can write a new method <code>rename_with_capitalization</code> and use <code>alias_method_chain</code> to resolve this:</p> <pre><code>class Person def rename_with_capitalization(name) rename_without_capitalization(name) self.first_name[0,1] = self.first_name[0,1].upcase self.last_name[0,1] = self.last_name[0,1].upcase end alias_method_chain :rename, :capitalization end </code></pre> <p>Now, the old <code>rename</code> is called <code>rename_without_capitalization</code>, and <code>rename_with_capitalization</code> is <code>rename</code>. For example:</p> <pre><code>person.rename("bob smith") person.first_name #=> Bob person.last_name #=> Smith person.rename_without_capitalization("tom johnson") person.first_name #=> tom person.last_name #=> johnson </code></pre>

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