Ruby: Syntax for defining a constant inside a Struct

Question

Consider the following (correct) Ruby program:

class Outer

  Inner = Struct.new(:dummy) do
    CONST = \'abce\'
    def fun
      puts(dummy)
    end
  end
         


        

Answer 1

This happens because the constant is defined in the current namespace. The class and module keywords define namespaces, but Struct.new (just like Class.new) does not.

In order to define the constant under the Struct's scope, you have to use self::

class Outer
  Inner = Struct.new(:dummy) do
    self::CONST = 'abce'
  end
end

Outer::Inner::CONST
#=> 'abce'

Outer::CONST
#=> NameError uninitialized constant Outer::CONST