我有一个超类，它是许多子类(Customer, Product, ProductCategory…)的父类(Entity)。
我想在Typescript中动态克隆一个包含不同子对象的对象。
例如:拥有不同产品的客户拥有一个ProductCategory
var cust:Customer = new Customer ();
cust.name = "someName";
cust.products.push(new Product(someId1));
cust.products.push(new Product(someId2));
为了克隆对象的整个树，我在实体中创建了一个函数
public clone():any {
var cloneObj = new this.constructor();
for (var attribut in this) {
if(typeof this[attribut] === "object"){
cloneObj[attribut] = this.clone();
} else {
cloneObj[attribut] = this[attribut];
}
}
return cloneObj;
}
当new被转译为javascript时，将引发以下错误:错误TS2351:不能对缺少调用或构造签名的表达式使用'new'。
虽然脚本工作，但我想摆脱转译错误
下面是deepCopy在TypeScript中的实现(代码中不包含任何内容):
const deepCopy = <T, U = T extends Array<infer V> ? V : never>(source: T ): T => {
if (Array.isArray(source)) {
return source.map(item => (deepCopy(item))) as T & U[]
}
if (source instanceof Date) {
return new Date(source.getTime()) as T & Date
}
if (source && typeof source === 'object') {
return (Object.getOwnPropertyNames(source) as (keyof T)[]).reduce<T>((o, prop) => {
Object.defineProperty(o, prop, Object.getOwnPropertyDescriptor(source, prop)!)
o[prop] = deepCopy(source[prop])
return o
}, Object.create(Object.getPrototypeOf(source)))
}
return source
}
解决具体问题
你可以使用类型断言来告诉编译器你知道的更好:
public clone(): any {
var cloneObj = new (this.constructor() as any);
for (var attribut in this) {
if (typeof this[attribut] === "object") {
cloneObj[attribut] = this[attribut].clone();
} else {
cloneObj[attribut] = this[attribut];
}
}
return cloneObj;
}
克隆
截至2022年，有一项提案允许structuredClone深度复制许多类型。
const copy = structuredClone(value)
对于你可以在什么事情上使用它有一些限制。
请记住，有时候编写自己的映射比完全动态的映射更好。然而，你可以使用一些“克隆”技巧来获得不同的效果。
我将使用以下代码的所有后续示例:
class Example {
constructor(public type: string) {
}
}
class Customer {
constructor(public name: string, public example: Example) {
}
greet() {
return 'Hello ' + this.name;
}
}
var customer = new Customer('David', new Example('DavidType'));
选择1:分散
属性:是的
方法:没有
深度复制:否
var clone = { ...customer };
alert(clone.name + ' ' + clone.example.type); // David DavidType
//alert(clone.greet()); // Not OK
clone.name = 'Steve';
clone.example.type = 'SteveType';
alert(customer.name + ' ' + customer.example.type); // David SteveType
选项2:Object.assign
属性:是的
方法:没有
深度复制:否
var clone = Object.assign({}, customer);
alert(clone.name + ' ' + clone.example.type); // David DavidType
alert(clone.greet()); // Not OK, although compiler won't spot it
clone.name = 'Steve';
clone.example.type = 'SteveType';
alert(customer.name + ' ' + customer.example.type); // David SteveType
选项3:Object.create
属性:继承
方法:继承
深度复制:浅继承(深度更改同时影响原始和克隆)
var clone = Object.create(customer);
alert(clone.name + ' ' + clone.example.type); // David DavidType
alert(clone.greet()); // OK
customer.name = 'Misha';
customer.example = new Example("MishaType");
// clone sees changes to original
alert(clone.name + ' ' + clone.example.type); // Misha MishaType
clone.name = 'Steve';
clone.example.type = 'SteveType';
// original sees changes to clone
alert(customer.name + ' ' + customer.example.type); // Misha SteveType
选项4:深度复制功能
属性:是的
方法:没有
深度复制:是的
function deepCopy(obj) {
var copy;
// Handle the 3 simple types, and null or undefined
if (null == obj || "object" != typeof obj) return obj;
// Handle Date
if (obj instanceof Date) {
copy = new Date();
copy.setTime(obj.getTime());
return copy;
}
// Handle Array
if (obj instanceof Array) {
copy = [];
for (var i = 0, len = obj.length; i < len; i++) {
copy[i] = deepCopy(obj[i]);
}
return copy;
}
// Handle Object
if (obj instanceof Object) {
copy = {};
for (var attr in obj) {
if (obj.hasOwnProperty(attr)) copy[attr] = deepCopy(obj[attr]);
}
return copy;
}
throw new Error("Unable to copy obj! Its type isn't supported.");
}
var clone = deepCopy(customer) as Customer;
alert(clone.name + ' ' + clone.example.type); // David DavidType
// alert(clone.greet()); // Not OK - not really a customer
clone.name = 'Steve';
clone.example.type = 'SteveType';
alert(customer.name + ' ' + customer.example.type); // David DavidType
