Passing class as parameter causes "is not newable" error

Question

I'm trying to pass a class as a parameter to some function, that will instantiate this class and return it. Here is my code:

module A.Views {   export class View { ... } }  module A.App {   export class MyApp {     ...     registerView(viewKlass:A.Views.View):void     {         var test = new viewKlass;     }    } } 

When i'm trying to compile this, i'm getting:

(...): Value of type 'Views.View' is not newable. 

What am I doing wrong?

If a newable type value is an object constructor how do i pass the constructor function at runtime?

Answer 1

We need something to say typeof(MyClass) to distinguish objects from classes in function signatures.

Anyway, you can actually solve you problem by using constructor type signature. Considering this class:

class MyClass {     constructor (private name: string) {     } } 

To pass that class as a type that you can then instantiate in a function, you actually have to duplicate the class constructor signature like this:

function sample(MyClass: new (name: string) => MyClass) {     var obj = new MyClass("hello"); } 

EDIT : There is a simple solution found on codeplex:

You have to create an interface for your class like this:

interface IMyClass {     new (name: string): MyClass; } 

Then, use it in your function signature:

function sample(MyClass: IMyClass) {     var obj = new MyClass("hello"); }