创建型设计模式-原型 Prototype

简介

原型模式支持按照一个对象为模板，创建出另一个一模一样的对象。

简单说就是把 A 对象的属性，都赋值到 B 上，注意必须是深拷贝，即 clone 后的 AB 关联的对象是不同的对象。

角色

• 抽象原型类

  定义 clone 方法

• 具体实现类

  实现 clone 方法

类图

代码

class Prototype
{
    public $primitive;
    public $component;
    public $circularReference;

    public function __clone()
    {
        $this->component = clone $this->component;

        $this->circularReference = clone $this->circularReference;
        $this->circularReference->prototype = $this;
    }
}

class ComponentWithBackReference
{
    public $prototype;

    public function __construct(Prototype $prototype)
    {
        $this->prototype = $prototype;
    }
}

function clientCode()
{
    $p1 = new Prototype();
    $p1->primitive = 245;
    $p1->component = new \DateTime();
    $p1->circularReference = new ComponentWithBackReference($p1);

    $p2 = clone $p1;
    if ($p1->primitive === $p2->primitive) {
        echo "Primitive field values have been carried over to a clone. Yay!\n";
    } else {
        echo "Primitive field values have not been copied. Booo!\n";
    }
    if ($p1->component === $p2->component) {
        echo "Simple component has not been cloned. Booo!\n";
    } else {
        echo "Simple component has been cloned. Yay!\n";
    }

    if ($p1->circularReference === $p2->circularReference) {
        echo "Component with back reference has not been cloned. Booo!\n";
    } else {
        echo "Component with back reference has been cloned. Yay!\n";
    }

    if ($p1->circularReference->prototype === $p2->circularReference->prototype) {
        echo "Component with back reference is linked to original object. Booo!\n";
    } else {
        echo "Component with back reference is linked to the clone. Yay!\n";
    }
}

clientCode();

output:

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!