Question

I mean, I want to create a class method in my module that will be used by the class who includes the module. They are in separated files.

By far I have something like this:

module Base
  def self.all
    puts "All Users"
  end
end

class User
  include Base
end

But I’m getting: NoMethodError: undefined methodall’ for User:Class`

Can you please explain the problem and if what I’m doing is a bad practice or going against any principle?

Answer 1

You can extend the module in your class, your code should be like this:

module Base
  def all
    puts "All Users"
  end
end

class User
  extend Base
end

When you do something like this:

module MyModule
  def self.module_method
    puts "module!"
  end
end

You’re actually adding the method in the module itself, you could call the previous method like this:

MyModule.module_method

There is a way to just include the module and get the behaviour that you want, but I don’t think this could be considered the “way to go”. Look at the example:

module Base
  def self.included(klass)
    def klass.all
      puts "all users"
    end
  end
end

class User
  include Base
end

But like I said, if you can go with the extend class method, it is a better suit.