How can I export an interface that I have imported?

Question

I am creating a library in typescript, which is spread across multiple files. I take all the classes and constants I have defines and import them into one module, which exports them all under one namespace. I have just defines an interface, and I wish to include it in the same namespace/module as all the other parts of my library. But apparently I can't.

Here's a simplified example:

/app.ts is the entry point of the application, all I do in it at the moment is include my library MyLib:

//app.ts
import myLib = require("lib/MyLib/MyLib"); // this works fine

/lib/MyLib/MyLib.ts is the file in which I import all of the things defined by MyLib, and export them together:

// lib/MyLib/MyLib.ts

import VehiclesImport = require("./transport/vehicles");
// error under  VehiclesImport.IAutomobile, saying that VehiclesImport has no property IAutomobile
export var IAutomobile = VehiclesImport.IAutomobile; 
export var Car = VehiclesImport.Car;

In /lib/MyLib/transport/vehicles.ts, I define several classes and interfaces of vehicles, here, I'll just show IAutomobile and Car:

// lib/MyLib/transport/vehicles.ts

export interface IAutomobile {
    weight: number
}

export class Car implements IAutomobile {
    weight = 3000
}

I have tried creating a class truck in MyLib.ts, which properly implements IAutomobile, and that works fine, without any error messages. The problem only seems to arise when I want to access IAutomobile outside of an 'implements' statement.

I apologize if this seems like a 'code dump', but in my opinion, this is a serious problem that I cannot access my interfaces except in a class declaration. I have searched Google for the past two hours and found nothing on the subject. Thanks for any help you can give me!

Edit: I understand that typescript interfaces are not part of the compiled javascript code, but that should not stop me from manipulating them within typescript.

Answer 1

Use the import keyword to bring in something into the type declaration space (as opposed to var which brings it into the variable declaration space).

This is demonstrated below. a.ts:

export interface A {
    val: number;
}

To re-export this from another file b.ts:

import a = require('./a');
export import B = a.A; // Important use of import

Sample usage in some other file c.ts:

import b = require('./b');

var foo: b.B;
foo.val = 123;

interface C extends b.B {
    val2:number;
}

var bar: C;
bar.val2 = 456;