How to reject a promise on NativeScript - Angular 2

Question

I have a code that works in angular 2, but when I try to use it in a nativescript project fails. I´m trying to reject a promise like this:

login(credentials:Credentials):Promise<User> {
    if (!valid) {
         return Promise.reject<User>("Invalid password");
    }else {
         return Promise.resolve(new User("some user"));
    }
}

And I get this error:

Error:(32, 22) TS2346: Supplied parameters do not match any signature of call target.

Answer 1

You missed to return promise when you Rejected it. Error directly says that you aren't returning Promise<User> from function. As method return type is Promise<User> , it always return that object.

PS: After edit in OP found that method can return two types of data, on success it would be User object, on reject its string . So for such case I'd prefer you to change the method return type to User | string User | string

Code

login(credentials:Credentials):Promise<User | string> {
    if (!valid) {
         //returned promise here which was missing and failing compilation
         return Promise.reject("Invalid password");
    }else {
         return Promise.resolve(new User("some user"));
    }
}