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原型

原型在 Ruby 中的实现

原型是一种创建型设计模式 使你能够复制对象 甚至是复杂对象 而又无需使代码依赖它们所属的类

所有的原型类都必须有一个通用的接口 使得即使在对象所属的具体类未知的情况下也能复制对象 原型对象可以生成自身的完整副本 因为相同类的对象可以相互访问对方的私有成员变量

进一步了解原型模式

在 Ruby 中使用模式

复杂度

流行度

使用示例 Ruby 的 Cloneable  克隆 接口就是立即可用的原型模式

识别方法 原型可以简单地通过 clone copy 等方法来识别

概念示例

本例说明了原型设计模式的结构并重点回答了下面的问题

  • 它由哪些类组成
  • 这些类扮演了哪些角色
  • 模式中的各个元素会以何种方式相互关联

main.rb: 概念示例

# The example class that has cloning ability. We'll see how the values of field
# with different types will be cloned.
class Prototype
  attr_accessor :primitive, :component, :circular_reference

  def initialize
    @primitive = nil
    @component = nil
    @circular_reference = nil
  end

  # @return [Prototype]
  def clone
    @component = deep_copy(@component)

    # Cloning an object that has a nested object with backreference requires
    # special treatment. After the cloning is completed, the nested object
    # should point to the cloned object, instead of the original object.
    @circular_reference = deep_copy(@circular_reference)
    @circular_reference.prototype = self
    deep_copy(self)
  end

  # deep_copy is the usual Marshalling hack to make a deep copy. But it's rather
  # slow and inefficient, therefore, in real applications, use a special gem
  private def deep_copy(object)
    Marshal.load(Marshal.dump(object))
  end
end

class ComponentWithBackReference
  attr_accessor :prototype

  # @param [Prototype] prototype
  def initialize(prototype)
    @prototype = prototype
  end
end

# The client code.
p1 = Prototype.new
p1.primitive = 245
p1.component = Time.now
p1.circular_reference = ComponentWithBackReference.new(p1)

p2 = p1.clone

if p1.primitive == p2.primitive
  puts 'Primitive field values have been carried over to a clone. Yay!'
else
  puts 'Primitive field values have not been copied. Booo!'
end

if p1.component.equal?(p2.component)
  puts 'Simple component has not been cloned. Booo!'
else
  puts 'Simple component has been cloned. Yay!'
end

if p1.circular_reference.equal?(p2.circular_reference)
  puts 'Component with back reference has not been cloned. Booo!'
else
  puts 'Component with back reference has been cloned. Yay!'
end

if p1.circular_reference.prototype.equal?(p2.circular_reference.prototype)
  print 'Component with back reference is linked to original object. Booo!'
else
  print 'Component with back reference is linked to the clone. Yay!'
end

output.txt: 执行结果

Primitive field values have been carried over to a clone. Yay!
Simple component has been cloned. Yay!
Component with back reference has been cloned. Yay!
Component with back reference is linked to the clone. Yay!

原型在其他编程语言中的实现

原型在 Java 中的实现 原型在 C# 中的实现 原型在 PHP 中的实现 原型在 Python 中的实现 原型在 Swift 中的实现 原型在 TypeScript 中的实现