Ruby 原型模式讲解和代码示例
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。
复杂度：
流行度：
使用示例： Ruby 的 dup或 clone方法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或 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!
