Question

Trying to inject my own function (say check) to Float class. When I am doing from a module it is not injected to Float class. Please see the following snippets.

irb(main):001:0> module QA
irb(main):002:1>   class Float
irb(main):003:2>     def self.check
irb(main):004:3>     end
irb(main):005:2>   end
irb(main):006:1> end
=> nil
irb(main):007:0> include QA
=> Object
irb(main):008:0> Float.respond_to?(:check)
=> false
irb(main):009:0> extend QA
=> main
irb(main):010:0> Float.respond_to?(:check)
=> false
irb(main):011:0> class Float
irb(main):012:1>   def self.check
irb(main):013:2>   end
irb(main):014:1> end
=> nil
irb(main):015:0> Float.respond_to?(:check)
=> true

Answer 1

This:

module QA
  class Float
    def self.check
    end
  end
end

Is creating/modifying the class QA::Float, not Float. Try doing

QA::Float.respond_to?(:check)

And you’ll see.

You could do something like this instead:

module QA
    def self.included(klass)
        Float.class_eval "def self.check;end"
    end
end

include QA
Float.respond_to?(:check)
# true

Some useful references:

• class_eval
• included