TypeScript basic programming : interface issue

Question

Just trying to learn TypeScript.

Not sure why I'm still getting below error.

Note: I have tried meeting all the requirements of interface

interface Greet {
    greet(name?: Greet): string;
    (val: string): string;
}


class Person implements Greet {

    greet(name?: Greet): string {
        return 'Hello ' + name;
    }

    obj(val: string):string {
        return 'Hello';
    };


}

Error

TsFiles/OopsTest.ts(8,7): error TS2420: Class 'Person' incorrectly implements interface 'Greet'.
  Type 'Person' provides no match for the signature '(val: string): string'
8:26:50 PM - Compilation complete. Watching for file changes.

Answer 1

If you're trying to create a hybrid type then, per the documentation, the implementation should look something like:

function getPerson(): Greet {
    let person = <Greet>function(val: string) { return '' };
    person.greet = function(name?: Greet) { return '' };
    return person;
}

Having (val: string): string; in the interface requires the implementation of Greet to be a function, not a class.

Answer 2

interface Greet {
    greet(name?: Greet): string;
    obj(val: string): string; // <<<=== `obj` missing
}