Ruby Study 14 : Modules - Digging Deeper

Creates module functions for the named methods. These functions may be called with the module as a receiver, and also become available as instance methods to classes that mix in the module. Module functions are copies of the original, and so may be changed independently. The instance-method versions are made private. If used with no arguments, subsequently defined methods become module functions.

也就是说使用module_function带参数时, 将复制原来这个module中定义的instance method, 作为module singleton method. 并且被复制的instance method可以override 而不会影响已经复制的module singleton method.

如果module_function不带参数, 则表示这后面创建的都是module singleton method.

module Mod

  def one

    "This is one"

  end

  module_function :one  # 带一个参数:one, 表示复制one这个instance method为module singleton method

end



class Cls

  include Mod

  def call_one

    one

  end

end



p Mod.one     #=> "This is one"

c = Cls.new

p c.call_one  #=> "This is one"



module Mod

  def one

    "This is the new one"

  end

end



p Mod.one     #=> "This is one"

p c.call_one  #=> "This is the new one"

module Mod
  def one
    "This is one"
  end
  module_function
  def two
     return "This is two"
  end
  def three
     return "This is three"
  end
end

class Myclass
   include Mod
end

ob = Myclass.new
p ob.one  #=>  "This is one"
p Mod.two  #=>  "This is two"
p Mod.three  #=>  "This is three"

p ob.two  # 报错, 因为module_function没带参数的话, 后面定义的method就是module singleton method
C:/Users/digoal/Desktop/new.rb:20:in `<main>': private method `two' called for #<Myclass:0x208a940> (NoMethodError)

module Mod
  def hello
    "Hello from Mod.\n"
  end
end

class Klass
  def hello
    "Hello from Klass.\n"
  end
end

k = Klass.new
p k.hello         #=> "Hello from Klass.\n"
k.extend(Mod)   #=> #<Klass:0x401b3bc8> , Mod的hello方法将覆盖掉k对象的hello方法.
p k.hello         #=> "Hello from Mod.\n"
n = Klass.new
p n.hello  #=> "Hello from Klass.\n"  # 其他对象不会受到影响
结果
"Hello from Klass.\n"
"Hello from Mod.\n"
"Hello from Klass.\n"

module A
    def method_y
        puts( 'hello from method_y of module A' )
    end
end

module B
    def method_x
        puts( 'hello from method_x of module B' )
    end
end

module C
    def method_x
        puts( 'hello from method_x of module C' )
    end
end

class Myclass
    def method_y
        puts( 'hello from method_y of class Myclass' )
    end
end

ob = Myclass.new
ob.extend(A)
ob.method_y       #=> hello from method_y of module A
ob.extend(B)
ob.method_y       #=> hello from method_y of module A
ob.method_x       #=> hello from method_x of module B
ob.extend(C)
ob.method_y       #=> hello from method_y of module A
ob.method_x       #=> hello from method_x of module C

ob = Myclass.new
ob.extend(A,B,C)
ob.method_y       #=> hello from method_y of module A
ob.method_x       #=> hello from method_x of module B  , 注意这里是扩展的B模块的method_x方法, 而不是C里面的.

freeze → obj click to toggle source 
Prevents further modifications to obj. A RuntimeError will be raised if modification is attempted. There is no way to unfreeze a frozen object. See also Object#frozen?. 

This method returns self. 

   a = [ "a", "b", "c" ]
   a.freeze
   a << "z"
produces: 

   prog.rb:3:in `<<': can't modify frozen array (RuntimeError)
    from prog.rb:3

ob = Myclass.new
ob.freeze
ob.extend(A,B,C)
报错
C:/Users/digoal/Desktop/new.rb:27:in `extend_object': can't modify frozen object (RuntimeError)
 from C:/Users/digoal/Desktop/new.rb:27:in `extend'
 from C:/Users/digoal/Desktop/new.rb:27:in `<main>'

ob = Myclass.new
ob.freeze
def ob.newmethod
   puts("this is a new ob's singleton method")
end
报错
C:/Users/digoal/Desktop/new.rb:27:in `<main>': can't modify frozen Myclass (RuntimeError)

ob = Myclass.new
p ob.frozen?  #=> false
ob.freeze
p ob.frozen?  #=> true