Justin Justin - 2 months ago 59
TypeScript Question

Typescript: Cannot invoke an expression whose type lacks a call signature

I am brand new to typescript, and I have two classes. In the parent class I have:

abstract class Component {
public deps: any = {};
public props: any = {};

public setProp(prop: string): any {
return <T>(val: T): T => {
this.props[prop] = val;
return val;
};
}
}


In the child class I have:

class Post extends Component {
public toggleBody: string;

constructor() {
this.toggleBody = this.setProp('showFullBody');
}

public showMore(): boolean {
return this.toggleBody(true);
}

public showLess(): boolean {
return this.toggleBody(false);
}
}


Both showMore and ShowLess give me the error, "Cannot invoke an expression whose type lacks a call signature."

But the function that setProp returns DOES have a call signature, I think? I think I'm misunderstanding something important about typings of functions, but I don't know what it is.

Thanks!

Answer

The function that it returns has a call signature, but you told Typescript to completely ignore that by adding : any in its signature.

Don't do that.

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