在另一个类中使用模块的类

Question

I'm creating a gem:

module Core
  require "lib/doctor"
  require "lib/slot"
end

module Core
  class Doctor
    def message
      puts Slot.message
    end
  end
end

module Core
  class Slot
    def message
      return "Hello World"
    end
  end
end

If I use the gem I obtain:

Gem Load Error is: uninitialized constant Core::Doctor::Slot

Answer 1

As you can see from your error, ruby is trying to load the constant Slot in the context of Core::Doctor . But, you want Slot in the context of Core . So, try:

module Core
  class Doctor
    def message
      puts Core::Slot.message
    end
  end
end

Also, here:

puts Core::Slot.message

you're trying to call message as a class method. However, here:

module Core
  class Slot
    def message
      return "Hello World"
    end
  end
end

you're defining message as an instance method.

If you want message to be a class method, you'll need to do:

module Core
  class Slot
    def self.message
      return "Hello World"
    end
  end
end

or

module Core
  class Slot
    class << self
      def message
        return "Hello World"
      end
    end
  end
end

(depending on your preference). If you want keep message as an instance method, then you'll need to do:

puts Core::Slot.new.message