jameshfisher jameshfisher - 2 months ago 13
Ruby Question

(In Ruby) allowing mixed-in class methods access to class constants

I have a class with a constant defined for it. I then have a class method defined that accesses that class constant. This works fine. An example:

#! /usr/bin/env ruby

class NonInstantiableClass
Const = "hello, world!"
class << self
def shout_my_constant
puts Const.upcase
end
end
end

NonInstantiableClass.shout_my_constant


My problem arises in attempting to move this class method out to an external module, like so:

#! /usr/bin/env ruby

module CommonMethods
def shout_my_constant
puts Const.upcase
end
end

class NonInstantiableClass
Const = "hello, world!"
class << self
include CommonMethods
end
end

NonInstantiableClass.shout_my_constant


Ruby interprets the method as requesting a constant from the module, rather than the class:

line 5:in `shout_my_constant': uninitialized constant CommonMethods::Const (NameError)


So, what magic tricks do you fellows have to let the method access the class constant? Many thanks.

Answer

This seems to work:

#! /usr/bin/env ruby

module CommonMethods
    def shout_my_constant
        puts self::Const.upcase
    end
end

class NonInstantiableClass
    Const = "hello, world!"
    class << self
        include CommonMethods
    end
end

NonInstantiableClass.shout_my_constant

HTH