Typescript assign generic type to variable

Question

When trying to assign a generic type to Type<any>, i cannot get the type constraint correct when i know the type is an angular component.

However directly assigning a component type works.

This works

private routeComponent: Type<any>;
public component<TComponent>(): RouteBuilder {
    this.routeComponent = HomeComponent;
    return this;
}

This doesnt.

private routeComponent: Type<any>;
public component<TComponent>(): RouteBuilder {
    this.routeComponent = TComponent;
    return this;
}

It fails with

error TS2693: 'TComponent' only refers to a type, but is being used as a value here.

How can i make it so my component method accepts only a Component, or if cant do that at least be able to assign the generic type to the Type<any> the same as i can if i do it direct.

Titian Cernicova-Dragomir · Accepted Answer · 2017-11-22 11:30:44Z

1

Generics are implemented in Typescript using type erasure, so at runtime TComponent will not available. You can pass the class as an argument to the function instead :

public component<TComponent>(type: Type<TComponent>): RouteBuilder {
    this.routeComponent = type;
    return this;
}
component(HomeComponent);

answered Nov 22, 2017 at 11:30

Titian Cernicova-Dragomir

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1 Comment

Richard Friend Over a year ago

Excellent! just what i was looking for, thanks very much

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