Question

我有一个模块Top，其中包含模块A和B。在每个中，我想使用模块C的类方法。为此，我必须为每个模块C和A添加B。是否可以在C中包含Top，以便所有子模块都可以访问其类方法？

示例：

# I'll extend module C in example to make it shorter

module C
  def foo; puts 'Foo!' end
end

module Top
  extend C

  module A  end
  module B  end
end

# That's how it works now

Top.foo
#=> "Foo!"
Top::A.foo
#=> NoMethodError: undefined method `foo' for Top::A:Module
Top::B.foo
#=> NoMethodError: undefined method `foo' for Top::B:Module

# That's how I want it to work

Top.foo
#=> "Foo!"
Top::A.foo
#=> "Foo!"
Top::B.foo
#=> "Foo!"

Answer 1

实际上很可能是这样的 OP更新了代码，所以这是我的实现：

class Module
  def submodules
    constants.collect {|const_name| const_get(const_name)}.select {|const| const.class == Module}
  end
end


module C
  # this gets called when the module extends another class or module
  # luckily it does _not_ get called when we extend via :send
  def self.extended(base)
    # collect all submodules and extend them with self
    base.submodules.each{|m| m.send :extend, self }
  end
  def c1
    puts "c1"
  end
end

module Top
  module A;end
  module B;end
  # extend needs to go at the end - otherwise Top doesnt know about its submodules
  extend C
end

Top.c1     # => "c1"
Top::A.c1  # => "c1"
Top::B.c1  # => "c1"

Answer 2

没有内置方式。你必须实现它：

class Module
  def extend_each_module m
    constants.each do |sym|
      const_get(sym).instance_eval{extend(m) if kind_of?(Module)}
    end
  end
end

module C
  def foo
    puts "Foo!"
  end
end

module Top
  module A; end
  module B; end
  extend C
  extend_each_module C
end

Top.foo
# => Foo!
Top::A.foo
# => Foo!
Top::B.foo
# => Foo!

如何在嵌套子模块中自动包含模块

2 个答案: