如何指定类构造函数的返回类型（例如使用代理）？

Question

I'm pretty new to the Typescript world. Trying around with it a little more I stumbled across a problem when using a Proxy as a returned value from a class constructor.

Imagine the following code:

class Container {
  constructor() {
    return new Proxy(this, containerProxyHandler);
  }
}

const container = new Container();

container.sessionStorage = () => {
  return new SessionStorage('SESSION_ID');
};

container.session = factory(() => {
  return new Session(container.sessionStorage);
});

container.random = protected(() => {
  return Math.random();
});

The Container type is intended to be used as a dependency injection container. So assigning the properties inside the Container class is not possible due to the variable amount of services it will store.

When validated it complains about missing properties sessionStorage , session and random inside the Container type when assigning arrow functions to them.

Property 'sessionStorage' does not exist on type 'Container'

I could of course assign a type to the container variable myself via as or use a factory function, but find this approaches cumbersome for other people to use for example in case of library.

const container = new Container() as { [key: string]: any };

Is there an easier solution for this without the need of extra boilerplate code?

Answer 1

You can create an interface for it:

interface SomeType { 
  [name: string]: any; 
}