Guidelines on declining a pledge in NativeScript with Angular 2

Question

Guidelines on declining a pledge in NativeScript with Angular 2

I have encountered an issue with my code in Angular 2. It works fine in that framework, but when I tried using it in a Nativescript project, it failed to work properly. The problem arises when I attempt 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"));
    }
}

This results in the following error message:

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

javascript angular typescript nativescript angular2-nativescript

Answer 1

Answer №1

Remember to always return a promise when rejecting it. The error message clearly states that the function is not returning a Promise<User>. Since the method's return type is Promise<User>, it should always return an object of that type.

PS: Upon further editing, it was discovered that the method can return two different types of data. In case of success, it should return a User object, and in case of rejection, a string. Therefore, it is recommended to change the method's return type to User | string.

Code

login(credentials:Credentials):Promise<User | string> {
    if (!valid) {
         //Added missing return statement for the rejected promise
         return Promise.reject("Invalid password");
    }else {
         return Promise.resolve(new User("some user"));
    }
}

Answer 2

Remember to always return a promise when rejecting it. The error message clearly states that the function is not returning a Promise<User>. Since the method's return type is Promise<User>, it should always return an object of that type.

PS: Upon further editing, it was discovered that the method can return two different types of data. In case of success, it should return a User object, and in case of rejection, a string. Therefore, it is recommended to change the method's return type to User | string.

Code

login(credentials:Credentials):Promise<User | string> {
    if (!valid) {
         //Added missing return statement for the rejected promise
         return Promise.reject("Invalid password");
    }else {
         return Promise.resolve(new User("some user"));
    }
}

Guidelines on declining a pledge in NativeScript with Angular 2

Answer №1

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