Typescript: 'Cannot find name' error of imported class

Question

I have a file a.ts which contains a class A inside a module:

module moduleA {

  export class A {
  }

}

export = moduleA.A;

And another file b.ts which imports class A:

import A = require('a.ts');

class B {

  // This leads to an error: Cannot find name 'A'
  private test: A = null;

  constructor() {
    // But this is possible
    var xyz = new A();
  }
}

Interestingly, Typescript shows an error when I want to use A as a type in B. However, instantiating A does not lead to an error.

Can anybody explain me, why this is like that? Thank you very much!

Brocco · Accepted Answer · 2015-11-02 12:56:41Z

7

The use of the namespace module moduleA is not necessary... you can do this...

the keyword module is synonymous with namespace (C#) now... best practice is to use the ES6 style module structure which is basically each file is a module and export what you need and import what you need from elsewhere.

// a.ts
export class A {}

// b.ts
import { A } from './a';
class B {
  private test: A = null; // will not error now
  constructor () {
    var xyz = new A();
  }
}

Note: this is based upon TypeScript v1.5+

answered Nov 2, 2015 at 12:56

Brocco

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4 Comments

gizmodus Over a year ago

Thanks a lot for your answer! Though I need the module structure like this, because I have variables that must stay outside the class A but inside the module. Don't you think my solution should theoretically work like that?

JKillian Over a year ago

@user986305 You should still be able to declare variables outside the class but in the same file if you do things Brocco's way.

Brocco Over a year ago

@JKillian is correct, those variables will be contained to the scope of that file/module without being leaked externally.

gizmodus Over a year ago

Thanks JKilian and Brocco! I had it that way before with a variable "dependencies" in the various files. However, Typescript kept telling me that the variable "dependencies" was already declared with another type (in another file). Now I removed the modules as you described and it seems to work. I don't know if Typescript was not synced before or if it works now because I updated it. Anyways, to me the above problem is still not really solved to me. What do you think?

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