Infer types in generic class

Issue

Is it possible to infer types from a generic class?

In the example below I'd like to infer the types in the Component class to get the type and the value:

class Obj<T,V>{
    constructor(type: T, value: V){
        this.type = type;
        this.value = value;
    }
    type: T
    value: V
}
class TextObj extends Obj<"text" | "email", string>{
    
}

class Component<O extends Obj<infer F, infer V>> {
    constructor(obj: O){
        this.obj = obj;
    }

    obj: O
    
    getValue():V {
        return this.obj.value;
    }
    
    getType():F {
        return this.obj.type;
    }
}

class TextComponent extends Component<TextObj>{

}

let txtComp = new TextComponent(new TextObj("text", "some Text"));

let value = txtComp.getValue();
     //^--- should be string

available as TS Play

Solution

Instead of trying to infer type variables like this, you can access them indirectly. Since both are conveniently exposed as property types, you can use item access syntax:

class Component<O extends Obj<unknown, unknown>> {
    constructor(obj: O) {
        this.obj = obj;
    }

    obj: O

    getValue(): O['value'] {
        return this.obj.value;
    }

    getType(): O['type'] {
        return this.obj.type;
    }
}

Playground Link

Answered By - STerliakov