如何为属性创建TypeScript @enumerable（false）装饰器 [英] How to create a TypeScript @enumerable(false) decorator for a property

问题描述

我想在TypeScript中创建一个装饰器，以便能够使类属性不可枚举。

I want to create a decorator in TypeScript in order to be able to make a class property not enumerable.

我在这里找到了@enumerable的示例：
https://www.typescriptlang.org/docs/handbook/decorators .html＃method-decorators
，但这似乎仅适用于方法，不适用于属性：

I found an example of @enumerable here: https://www.typescriptlang.org/docs/handbook/decorators.html#method-decorators but that only seems to work for methods, not properties:

https://www.typescriptlang.org/docs/handbook/decorators.html#property-decorators

注意由于如何在$ b $中初始化属性装饰器，因此未将属性描述符作为
属性装饰器的参数提供b TypeScript。这是因为当前没有机制在定义原型成员
时描述实例属性
，也没有办法观察或修改属性的初始化程序。像
这样，属性装饰器只能用于观察已为类声明了特定名称的属性
。

NOTE  A Property Descriptor is not provided as an argument to a property decorator due to how property decorators are initialized in TypeScript. This is because there is currently no mechanism to describe an instance property when defining members of a prototype, and no way to observe or modify the initializer for a property. As such, a property decorator can only be used to observe that a property of a specific name has been declared for a class.

是否可以为类属性创建@enumerable装饰器？

Is there a way to create a @enumerable decorator for a class property?

谢谢

推荐答案

我最终得到了以下解决方案：

I ended up with this solution:

/**
 * @enumerable decorator that sets the enumerable property of a class field to false.
 * @param value true|false
 */
function enumerable(value: boolean) {
    return function (target: any, propertyKey: string) {
        let descriptor = Object.getOwnPropertyDescriptor(target, propertyKey) || {};
        if (descriptor.enumerable != value) {
            descriptor.enumerable = value;
            descriptor.writable= true;
            Object.defineProperty(target, propertyKey, descriptor)
        }
    };
}

用法：

class User {
    id:string;

    @enumerable(false)
    name: string;
}

测试：

   var user = new User();
   user.id = 1;
   user.name = 'John Doe';
   for (key in user){ console.log(key, user[key]);}

输出

id 1

不使用装饰器的相同测试

Same test without the use of the decorator

id 1
name John Doe

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