Illustrated Ruby: Modules

[WIP] Modules are the Ruby way to organise code.

Here’s a module with a method.

module MyModule
  def plus(a, b)
    a + b
  end
end

By using extend, we can inject the method in the current context.

extend MyModule
p plus(1, 2)

Constants can be obtained dynamically.

Object.const_get :INCREMENT

It is a SyntaxError to set a constant dynamically inside a method, but it is possible with const_set.

def decr(i)
  Object.const_set :DECREMENT, 1


  i - DECREMENT
end


p decr(5)

The constant is global. This would raise NameError if decr hadn’t been called.

p DECREMENT


$ ruby examples/modules/modules.rb
3
examples/modules/modules.rb:16:in `const_get': uninitialized constant INCREMENT (NameError)


Object.const_get :INCREMENT
      ^^^^^^^^^^
	from examples/modules/modules.rb:16:in `<main>'

by Loic Nageleisen | source | license