Can I add class methods and instance methods from the same module?

Question

Newbie question:

I know how include and extend work, what I am wondering is if there is a way to get both class and instance methods from a single module?

This is how I do it with two modules:

module InstanceMethods
    def mod1
        "mod1"
    end
end

module ClassMethods
    def mod2
        "mod2"
    end
end

class Testing
    include InstanceMethods
    extend ClassMethods 
end

t = Testing.new
puts t.mod1
puts Testing::mod2

Thanks for taking your time ...

Answer 1

There is a common idiom for that. It makes use of included object model hook. This hook gets invoked every time when a module is included to a module/class

module MyExtensions
  def self.included(base)
    # base is our target class. Invoke `extend` on it and pass nested module with class methods.
    base.extend ClassMethods
  end

  def mod1
    "mod1"
  end

  module ClassMethods
    def mod2
      "mod2"
    end
  end
end

class Testing
  include MyExtensions
end

t = Testing.new
puts t.mod1
puts Testing::mod2
# >> mod1
# >> mod2

I personally like to group instance method to a nested module as well. But this is less accepted practice, as far as I know.

module MyExtensions
  def self.included(base)
    base.extend ClassMethods
    base.include(InstanceMethods)

    # or this, if you have an old ruby and the line above doesn't work
    # base.send :include, InstanceMethods
  end

  module InstanceMethods
    def mod1
      "mod1"
    end
  end

  module ClassMethods
    def mod2
      "mod2"
    end
  end
end