How to call a method from a module of an other ruby file

Question

I have to Ruby files: one contains a module with some methods for statistical calculation, in the other file I want to call one of the methods in the module. How can I do that in Ruby?

Is that the right way?

require 'name of the file with the module'

a=[1,2,3,4]
a.method1

Solution 1

Require needs the absolute path to the file unless the file is located in one of Ruby's load paths. You can view the default load paths with puts $:. It is common to do one of the following to load a file:

Add the main file's directory to the load path and then use relative paths with require:

$: << File.dirname(__FILE__)
require "my_module"

Ruby 1.8 code that only loads a single file will often contain a one-liner like:

require File.expand_path("../my_module", __FILE__)

Ruby 1.9 added require_relative:

require_relative "my_module"

In the module you will need to define the methods as class methods, or use Module#module_function:

module MyModule
  def self.method1 ary
    ...
  end

  def method2
    ...
  end
  module_function :method2
end

a = [1,2,3,4]
MyModule.method1(a)

Solution 2

Your way is correct if your module file is in the require search path.

If your module provide methods to be used by the object itself, you must do:

require 'name of the file with the module'

a=[1,2,3,4]
a.extend MyModule   # here "a" can use the methods of MyModule
a.method1

See Object#extend.

Otherwise, if you'll use the methods directly by the module, you'll use:

MyModule.method1(a)