What is the difference between include and extend in Ruby?

Include vs Extend: Demystifying Ruby Mixins

<p>🤔 Just getting my head around Ruby metaprogramming. The mixin/modules always manage to confuse me. </p>

<p>So, what is the difference between include and extend in Ruby? Let's break it down! 🕵️‍♀️</p>

The Basics: Include and Extend

<ul> <li><strong>include</strong>: mixes in specified module methods as <strong>instance methods</strong> in the target class</li> <li><strong>extend</strong>: mixes in specified module methods as <strong>class methods</strong> in the target class</li> </ul>

<p>Essentially, when you include a module in a class, you are adding the module's methods as instance methods in that class. On the other hand, when you extend a class with a module, you are adding the module's methods as class methods in that class. 🎭</p>

🐉 A Bigger Dragon?

<p>Now, you may wonder if there's a bigger, hidden dragon behind this apparent simplicity. Let's find out! 🔍</p>

<pre><code>module ReusableModule def module_method puts "Module Method: Hi there!" end end class ClassThatIncludes include ReusableModule end class ClassThatExtends extend ReusableModule end puts "Include" ClassThatIncludes.new.module_method # "Module Method: Hi there!" puts "Extend" ClassThatExtends.module_method # "Module Method: Hi there!" </code></pre>

<p>As you can see from the code snippet above, when we include <code>ReusableModule</code> in <code>ClassThatIncludes</code>, we can directly call <code>module_method</code> on an instance of <code>ClassThatIncludes</code>.</p>

<p>Similarly, when we extend <code>ClassThatExtends</code> with <code>ReusableModule</code>, we can call <code>module_method</code> directly on the class itself, without creating any instances. 🎉</p>

Conclusion

<p>And that's the difference between include and extend in Ruby! 🎈</p>

<p>Use include when you want to add module methods as instance methods in a class, and extend when you want to add module methods as class methods in a class.</p>

<p>With this knowledge in hand, you can now confidently wield the power of mixins in your Ruby code. Happy coding! 💻</p>

<p>Got any other Ruby questions? Want to share your mixin adventures? Leave a comment below and let's start a conversation! 🗣️</p>