Decorator
Decorators make it possible to annotate and modify classes and properties at design time.
When To Use
You may use decorator with some reservation.
Why?
The decorator proposal has been in stage 2 for many years. While it is actively used as TypeScript and Babel supports it, it may change in the future.
Hoisting
When using decorator, you must beware of hoisting.
import { autoinject } from 'aurelia-dependency-injection'
@autoinject()
class Depender {
constructor(private dep: Dependent) { }
}
class Dependent {
}
Why?
Decorator executes at load time, at the point of declaration. This means all references it uses must be defined prior to the call.
The following code doesn't work:
dep parameter will receive undefined because the variable of class Dependent is hoisted but not the initialization.
Therefore, when the @autoinject() is called on the class Depender, the Dependent variable is still undefined.