Ruby/Rails nested module with same name

Question

Suppose I have a Bar module in the most out scope like this:

module Bar
  def hello
    puts('hello')
  end
end

and I also have another Bar module defined inside a Foo module like this:

module Foo
  module Bar
   def self.run
     Bar::hello
   end
  end
end

How can I include the hello method defined in the most outern Bar module to be used inside the Bar module defined inside the Foo module?

When trying to do this I'm getting:

NameError: uninitialized constant Foo::Bar::hello

steimo · Accepted Answer · 2022-08-07 17:29:47Z

2

You can extend top level module Bar and use :: constant prefix to start looking in the global namespace:

module Bar
  def hello
    puts('hello from top level Bar')
  end
end

module Foo
  module Bar
    extend ::Bar

    def self.run
      hello
    end
  end
end

Foo::Bar.run # >> hello from top level Bar

Or without extend:

module Bar
  def self.hello
    puts('hello from top level Bar')
  end
end

module Foo
  module Bar

    def self.run
      ::Bar.hello
    end
  end
end

Foo::Bar.run # >> hello from top level Bar

edited Aug 7, 2022 at 17:29

answered Aug 7, 2022 at 15:54

steimo

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1 Comment

Pavarine Over a year ago

Thanks for the two alternatives and for explaining about the :: constant prefix. Worked like charm!

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