如何使用类装饰器向类添加新属性? [英] How to add a new property to a class using class decorator?

问题描述

如何使用类装饰器向类添加新属性?

How can I add a new property to a class using a class decorator?

代码示例:

@MyClassDecorator
class MyClass {
    myFirstName: string;
    myLastName: string;
}

// I need something like this:
function MyClassDecorator (target: any): any {
    target['myNickname'] = 'Gambler';
}

let myClass = new MyClass();
console.log(myClass['myNickname']); // expecting "Gambler" but got "undefined"

如何修复此代码?

是否可以使用装饰器向类添加属性?

Is it possible at all to add a property to a class using decorator?

谢谢！

推荐答案

您需要将属性添加到原型而不是构造函数:

You need to add the property to the prototype and not the constructor:

function MyClassDecorator(target: any): any {
    target.prototype.myNickname = "Gambler";
}

这会让你得到你想要的，但问题是你将无法在没有打字稿抱怨的情况下访问这个属性:

That will get you what you want, but the problem is that you won't be able to access this property without typescript complaining:

let myClass = new MyClass();
console.log(myClass.myNickname); // error: Property 'myNickname' does not exist on type 'MyClass'

您可以尝试以下操作:

function myClassFactory(): MyClass & { myNickname: string } {
    return new MyClass() as MyClass & { myNickname: string };
}

let myClass = myClassFactory();
console.log(myClass.myNickname); // all good

(操场上的代码)

这篇关于如何使用类装饰器向类添加新属性?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！