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原型

原型在 TypeScript 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 TypeScript 中使用模式

复杂度

流行度

使用示例 TypeScript 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

index.ts: 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 {
    public primitive: any;
    public component: object;
    public circularReference: ComponentWithBackReference;

    public clone(): this {
        const clone = Object.create(this);

        clone.component = Object.create(this.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. Spread operator can be handy for this case.
        clone.circularReference = {
            ...this.circularReference,
            prototype: { ...this },
        };

        return clone;
    }
}

class ComponentWithBackReference {
    public prototype;

    constructor(prototype: Prototype) {
        this.prototype = prototype;
    }
}

/**
 * The client code.
 */
function clientCode() {
    const p1 = new Prototype();
    p1.primitive = 245;
    p1.component = new Date();
    p1.circularReference = new ComponentWithBackReference(p1);

    const p2 = p1.clone();
    if (p1.primitive === p2.primitive) {
        console.log('Primitive field values have been carried over to a clone. Yay!');
    } else {
        console.log('Primitive field values have not been copied. Booo!');
    }
    if (p1.component === p2.component) {
        console.log('Simple component has not been cloned. Booo!');
    } else {
        console.log('Simple component has been cloned. Yay!');
    }

    if (p1.circularReference === p2.circularReference) {
        console.log('Component with back reference has not been cloned. Booo!');
    } else {
        console.log('Component with back reference has been cloned. Yay!');
    }

    if (p1.circularReference.prototype === p2.circularReference.prototype) {
        console.log('Component with back reference is linked to original object. Booo!');
    } else {
        console.log('Component with back reference is linked to the clone. Yay!');
    }
}

clientCode();

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 Ruby 中的实现 原型在 Swift 中的实现