如何在TypeScript中使用通用类型初始化对象？

Question

I tried to do this like:

export class MapperObject<V> {
    public obj: V = {};
}

It does not work. Further I need to fill object like:

this.obj[key] = "1";

Without initialization it invokes an error.

Answer 1

The short answer is you can't do this in a type-safe way, because you don't know the fields of V that are required. You can force initialization by using a type assertion, but it's not exactly safe:

export class MapperObject<V> {
    public obj: V = {} as any;
}
let m = new MapperObject<{ requiredProp: string }>();
m.obj.requiredProp // undefined even though it is required

The safe solution is to have a constructor that requires the passing of a default for obj :

export class MapperObject<V> {         
    constructor(public obj: V) {}
}