Ruby模块可以被描述为单例类吗？ [英] Can a Ruby module be described as a singleton class?

问题描述

Ruby模块本质上只是一个只初始化一次的类，

包含MyModule

解决方案

一个ruby类是一个可以实例化的模块。像一个类，一个模块可以有方法，但你不能做一个模块的实例。这是他们之间的唯一区别。

在实践中，模块通常用于：

• 名字空格


• Mixins


• 保留功能

名称空间

以下是用作名称空间的模块的示例：

 模块MyLib 
 class Foo 
 end 
 class Bar 
 end 
 end 
  

这些类的全名是MyLib :: Foo和MyLib :: Bar。因为它们包含在命名空间（大概是唯一的）中，Foo和Bar的名称不能与您的程序或另一个库中定义的Foo或Bar发生冲突。

Mixin

这是一个用作混音的模块：

 模块Mixin 
 def foo 
 putfoo
 end 
 end 
  

由于您无法创建Mixin模块的实例，您可以通过包含（混合）模块来访问foo：

  class MyClass 
 include Mixin 
 end 
 
 MyClass.new.foo＃=> foo 
  

函数

模块可以容纳不在任何实例上操作的功能。为此，您可以在模块中定义类方法：

  module SomeFunctions 
 def self.foo 
 putfoo
 end 
 end 
  

模块中定义的类方法就像在类中定义的类方法一样。调用它：

  SomeFunctions.foo＃=> foo 
  

I'm trying to understand the purpose of a Ruby module from a design pattern perspective.

Is a Ruby module essentially just a class that is only initialized once?

include MyModule

解决方案

A ruby class is a module you can make instances of. Like a class, a module can have methods, but you cannot make an instance of a module. That's the only difference between them.

In practice, modules are commonly used for:

• Name spaces
• Mixins
• To hold functions

Name Space

Here's an example of a module used as a name space:

module MyLib
  class Foo
  end
  class Bar
  end
end

The full name of these classes is MyLib::Foo and MyLib::Bar. Because they are contained in a namespace (which presumably is unique), the names Foo and Bar cannot conflict with a Foo or Bar defined in your program or in another library.

Mixin

Here's a module used as a mix-in:

module Mixin
  def foo
    puts "foo"
  end
end

Since you can't make an instance of the Mixin module, you get access to foo by including (mixing in) the module:

class MyClass
  include Mixin
end

MyClass.new.foo    # => foo

Functions

Like a class, a module can hold functions that do not operate on any instance. To do that, you define class methods in the module:

module SomeFunctions
  def self.foo
    puts "foo"
  end
end

A class method defined in a module is just like a class method defined in a class. To call it:

SomeFunctions.foo    # => foo

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