在红宝石中使用包含的方法

Question

Suppose I have this

module Command
    extend ActiveSupport::Concern

      included do
        @path ||= File.join("#{file_path}", "some_file")
      end

      def file_path
        File.expand_path("some_other_file")
      end
...

When the module is included, I get undefined local variable or method file_path . So is there a way, to make the file_path method be recognized when the module is included ? (of course without putting file_path in the included method)

Answer 1

You are calling the method file_path ,in the method included , do..end block. That means with scope is set as Command class. But file_path is the instance_method,so Command.file_path is throwing an legitimate error. You have to call the method file_path ,on the instance of the class which is including the Command module. One example to illustrate this -

module A
    def self.included(mod)
        p foo
    end
    def foo
        2
    end
end

class B
    include A
end

# `included': undefined local variable or method `foo' for A:Module (NameError)

The error is coming because inside the method included self is A . A has no class method named as foo ,so the error comes out. Now to fix it we should call it as below:

module A
    def self.included(mod)
        p mod.new.foo
    end
    def foo
        2
    end
end

class B
    include A
end

# >> 2

Answer 2

You can try this :

module Command extend ActiveSupport::Concern

  def self.extended(klass)
    @path ||= File.join("#{klass.file_path}", "some_file")
  end

  def file_path
    File.expand_path("some_other_file")
  end

and then extend your module where you call it !