Is there a way to use class method in a module without extend it in rails?

Question

currently I have a module like this:

module MyModule
  def A

  end

  .....

end

and I have a model that I want to use that method A as a class method. However, the thing is I only need that A method. If I extend it, I am gonna extend the other unnecessary class methods into my model. Therefore, is there a way for me to do sth like MyModule.A without rewriting the module like this:

module MyModule
  def A
    ...
  end

  def self.A
    ...
  end

  .....

end

It is kind of repeating myself if I do it that way. I still feel there is a better way to do it in Rails.

Answer 1

Use Module#module_function to make a single function to be a module function:

module M
  def m1; puts "m1"; end
  def m2; puts "m2"; end
  module_function :m2
end

or:

module M
  def m1; puts "m1"; end
module_function # from now on all functions are defined as module_functions
  def m2; puts "m2"; end
end

M.m1 #⇒ NoMethodError: undefined method `m1' for M:Module
M.m2 #⇒ "m2"

Answer 2

Yes, you can define it as a module_function, then you should be able to access it using module name.

Ex:

module Mod
  def my_method
    100
  end

  def self.my_method_1
    200
  end
  module_function :my_method
end

Mod.my_method
# => 100
Mod.my_method_1
# => 200

Note: No need to add the self defined methods in module_function, they are accessible directly. But it's needed for methods defined without self