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打字稿 - 克隆对象

分类: 技术问答 • 2022-03-19 16:52:02

打字稿 - 克隆对象

问题描述：

我有一个超类，它是许多子类的父（实体）（ Customer ，产品， ProductCategory ...）

I have a super class that is the parent (Entity) for many subclass (Customer, Product, ProductCategory...)

我期待动态克隆包含Typescript中不同子对象的对象。

I'm looking to clone dynamically an object that contains different sub objects in Typescript.

例如：客户有不同的产品谁拥有 ProductCategory

In example : a Customer that has different Product who has a ProductCategory

var cust:Customer  = new Customer ();

cust.name = "someName";
cust.products.push(new Product(someId1));
cust.products.push(new Product(someId2));

为了克隆整个对象树，我在实体中创建了一个函数

In order to clone the whole tree of object I created a function in Entity 

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;
}

新上升当它被转换为javascript时出现以下错误：错误TS2351：不能对类型缺少调用或构造签名的表达式使用new。

The new rises the following error when it is transpiled to javascript: error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.

虽然脚本有效， 我想摆脱已发现的错误

Although the script works, I would like to get rid of the transpiled error

答

解决特定问题



您可以使用类型断言告诉编译器您更了解：

Solving The Specific Issue

You can use a type assertion to tell the compiler that you know better:

public clone(): any {
    var cloneObj = new (<any>this.constructor());
    for (var attribut in this) {
        if (typeof this[attribut] === "object") {
            cloneObj[attribut] = this.clone();
        } else {
            cloneObj[attribut] = this[attribut];
        }
    }
    return cloneObj;
}



克隆



请记住，有时候编写自己的映射会更好 - 而不是完全动态。但是，你可以使用一些克隆技巧给你带来不同的效果。

Cloning

Bear in mind that sometimes it is better to write your own mapping - rather than being totally dynamic. However, there are a few "cloning" tricks you can use that give you difference effects.

我将在后面的所有例子中使用以下代码：

I will use the following code for all the subsequent examples:

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'));

选项1：点差

属性： 是
方法：否
深层复制：否

Properties: Yes Methods: No Deep Copy: No

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

Option 2: Object.assign

属性：是
方法：否
深层复制：否

Properties: Yes Methods: No Deep Copy: No

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

Option 3: Object.create

属性：是
方法：是
深层复制：否

Properties: Yes Methods: Yes Deep Copy: No

var clone = Object.create(customer);

alert(clone.name + ' ' + clone.example.type); // David DavidType
alert(clone.greet()); // OK

clone.name = 'Steve';
clone.example.type = 'SteveType';

alert(customer.name + ' ' + customer.example.type); // David SteveType

选项4：深层复制功能

属性：是
方法：否
深层复制：是 

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 = <Customer>deepCopy(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

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