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Ruby Modules

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Include

3:05 with Jason Seifer

If we want to mix in behavior to a class, we have to use the include method. Unsurprisingly, based on the name, that will include all of the methods in the module in the class that we’re working with. In order to make our modules actually do something, it needs to be included in a class.

Code Samples

Here is our Fetcher module:

module Fetcher
  def fetch(item)
    puts "I'll bring that #{item} right back!"
  end
end

Once written, we can include that in the Dog class: 

class Dog
  include Fetcher
  attr_reader :name
  def initialize(name)
    @name = name
  end
end

dog = Dog.new("Fido")
dog.fetch("ball")

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    [SOUND]. 0:03
    We've learned how to write the simplest possible module. 0:04
    However, it really didn't do much of anything, 0:08
    because we were only talking about the namespacing aspect of modules. 0:11
    Next we're going to take a look at creating a mix-in. 0:16
    If we want to mix in behavior to a class, we have to use the include method. 0:20
    Unsurprisingly, based on the name, that will include all of the methods 0:25
    in the module in the class that we're working with. 0:30
    In order to make our modules actually do something, 0:34
    it needs to be included in a class. 0:37
    Let's see how that works now using workspaces. 0:40
    Okay, so let's go ahead and 0:45
    create our very first module that does something when we include it. 0:46
    So we're gonna call this fetcher.rb. 0:51
    And let's go ahead and create a class for a dog. 0:56
    And the dog is going to have a name. 1:03
    So we'll go ahead and create a new dog instance here. 1:11
    Here is Fido. 1:15
    Okay now we're gonna make a module, that we can include in the dog class, 1:17
    in case we wanted a dog to be able to fetch. 1:23
    So we'll call this module fetcher. 1:27
    And now we'll create a module called fetch, 1:32
    which is going to take one argument, which is the item that is being fetched. 1:36
    And then whatever is happening here we'll say, I'll bring that item right back. 1:42
    What we have to do is include the fetcher module in the Dog class. 1:49
    So, once we have this module here included in the Dog class, 1:58
    we can go back up here and any of the methods that are in this fetcher module 2:02
    will be included or mixed in to the Dog class and we have access to them. 2:08
    So we could now say something like dog.fetch, and 2:14
    then passing an item which is going to be ball. 2:18
    So if we run this, let's go ahead and see what happens. 2:22
    Dog says I'll bring that ball right back. 2:26
    Now the benefit for 2:29
    something like this is if we had another class, let's say, called Cat. 2:30
    We could say cat is Cat.new. 2:38
    What's a good name for a cat? 2:40
    So we'll create a new cat called Garfield, and 2:43
    now we can say cat.fetch laser pointer. 2:46
    So if we run that, because the Cat class includes the fetcher module, 2:52
    we get all of the methods inside of there. 2:56
    And if we run it again we can see that the cat says it's going to 3:00
    bring the laser pointer right back. 3:03

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