在运行时可以传递Typescript装饰器对象值吗？ [英] Is it possible to pass Typescript decorator object values in at runtime?

问题描述

我有一个类使用@MinDate约束这样装饰：

I have a class that is decorated with a @MinDate constraint like this:

export default class Order {
   purchaseDate: Date;
   @MinDate(this.purchaseDate)
   receiptDate: Date;
}

尝试验证 code>这是有效的验证错误。我的问题是将 this.purchaseDate 作为参数传递给 @MinDate（）装饰器。

When attempting to validate an instance of Order that is valid the validation errors out. My question is is it even possible / valid to pass in this.purchaseDate as an argument to the @MinDate() decorator.

换句话说，可以从对象中获取运行时值，还是在编译时必须使用这些值？所以例如：

In other words can typescript decorators receive runtime values from an object, or do these values have to be available at compile time? So for example:

@MinDate(new Date(12/22/2017));  //This should work?
@MinDate(this.someDate) // This will never work?

推荐答案

不，你不能这样做。 >
装饰器应用于类而不是实例，这意味着调用装饰器函数时没有这个。

No, you can't do that.
Decorators are applied to the classes and not the instances, meaning that there's no this when the decorator function is invoked.

使用静态值将起作用：

@MinDate(new Date(12/22/2017));

但是您不能使用实例成员。

But you can't use an instance member for it.

您可以在没有装饰器的构造函数中执行此操作：

You can do that in the constructor without a decorator:

export default class Order {
    ...
    constructor() {
        this.purchaseDate = ...
        this.receiptDate = this.purchaseDate;
    }
}

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