typescriptcocoscreator

Importing a default namespace - why am I getting "undefined"?

I try to learn typescript - make some first steps :). Here's my problem.

I created File1.ts as follows:

export namespace ex {
    export var mapper = ( ob : Object ) : NewClass {
        return ob as NewClass;
    };

    export class NewClass extends Object {
        public getSomething() : number {
            return 2;
        }
    };
}

Then, I created File2.ts, which uses the "mapper" defined in first file:

import { ex } from './Ex';

var a : Object = myAlreadyExistingObject;
console.log( ex.mapper( a ).getSomething() );

What I get:

ERROR: TypeError: File1_1.ex.mapper(a).getSomething is not a function.

The "Object" class is just an example - in reality I'm using an already defined, complex class. What I'm trying to achieve is to have "extension methods" like in C#, using it like this: ex.mapper( instance ).newFunction()

Why doesn't it work?

Solution 
  • return ob as NewClass;

    Type assertions in TypeScript don't cause runtime changes. If ob didn't have a getSomething method before, then the return value of this function won't either, and you'll get the error described.