Question

I have two files foo and bar. Foo implements class and initializes instance. Inside file bar.rb I want require foo.rb but also I want change implementation of Foo::Bar from foo.rb

dir tree

• foo.rb
• bar.rb

foo.rb

module Foo
  class Bar
    def random_method
      puts "Foo::Bar.random_method"
    end 
  end
end
Foo::Bar.new.random_method

bar.rb

#here I want overwrite Foo::Bar.random_method
require_relative 'foo' # so this line use new random_method

Answer 1

This is not possible (AFAIK), if you are not allowed to touch foo.rb.

# bar.rb

# redefine another random method (to be precise, define its first version)
module Foo
  class Bar
    def random_method
      puts 'another random method'
    end
  end
end

require_relative 'foo' # this will redefine the method and execute version from foo.rb

A possible approach is to split declaration of Foo::Bar and the code that uses it.

# foo_def.rb
module Foo
  class Bar
    def random_method
      puts "Foo::Bar.random_method"
    end 
  end
end

# foo.rb
require_relative 'foo_def'
Foo::Bar.new.random_method

# bar.rb
require_relative 'foo_def'

# replace the method here
module Foo
  class Bar
    def random_method
      puts 'another random method'
    end
  end
end

require_relative 'foo' # run with updated method