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
试试这个:
let copy = (JSON.parse(JSON.stringify(objectToCopy)));
这是一个很好的解决方案，直到您使用非常大的对象或对象具有不可序列化的属性。
为了保持类型安全，你可以在你想复制的类中使用一个copy函数:
getCopy(): YourClassName{
return (JSON.parse(JSON.stringify(this)));
}
或以静态的方式:
static createCopy(objectToCopy: YourClassName): YourClassName{
return (JSON.parse(JSON.stringify(objectToCopy)));
}
自从TypeScript 3.7发布以来，现在支持递归类型别名，它允许我们定义一个类型安全的deepCopy()函数:
// DeepCopy type can be easily extended by other types,
// like Set & Map if the implementation supports them.
type DeepCopy<T> =
T extends undefined | null | boolean | string | number ? T :
T extends Function | Set<any> | Map<any, any> ? unknown :
T extends ReadonlyArray<infer U> ? Array<DeepCopy<U>> :
{ [K in keyof T]: DeepCopy<T[K]> };
function deepCopy<T>(obj: T): DeepCopy<T> {
// implementation doesn't matter, just use the simplest
return JSON.parse(JSON.stringify(obj));
}
interface User {
name: string,
achievements: readonly string[],
extras?: {
city: string;
}
}
type UncopiableUser = User & {
delete: () => void
};
declare const user: User;
const userCopy: User = deepCopy(user); // no errors
declare const uncopiableUser: UncopiableUser;
const uncopiableUserCopy: UncopiableUser = deepCopy(uncopiableUser); // compile time error
操场上
