How to specify a generic type for a variable in Typescript

When attempting to assign a generic type to Type<any>, I am unable to correctly set the type constraint when I know it is an Angular component.

However, directly assigning a component type does work.

Here is an example that works:

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

This, on the other hand, does not work:

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

It results in the following error:

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

How can I modify my component method to only accept a Component, or if that is not achievable, how can I successfully assign the generic type to Type<any> like I can when doing it directly?

angulartypescriptgenerics

Answer №1

In Typescript, Generics are utilized with type erasure which means that at runtime the TComponent will not be accessible. One way to work around this limitation is by passing the class as a parameter to the function like so: 

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

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