[SOLVED] Is it possible to pass Typescript decorator object values in at runtime?

Is it possible to pass Typescript decorator object values in at runtime?

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

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

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.

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?

Solution

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.

Using a static value will work:

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

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

You can do that in the constructor without a decorator:

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