What is preventing me from setting the User object to null in my Angular application?

Currently, I am working on a project in Angular and encountering a specific issue.

In my service class, the structure looks like this:

export class AuthService {
    authchange: new Subject<boolean>();
    private user: User;

    registerUser(authData: AuthData) {
        this.user = {
            email: authData.email,
            userId: Math.round(Math.random() * 1000).toString()
        };
    }

    login(authData: AuthData) {
        this.user = {
            email: authData.email,
            userId: Math.round(Math.random() * 1000).toString()
        };
    }

    logout() {
        this.user = null;
    }

    getUser() {
        return { ...this.user };
    }

    isAuth() {
        return this.user != null;
    }
}

Essentially, there is a custom User object defined within the code:

private user: User;

then there is a method implemented as follows:

logout() {
    this.user = null;
}

where an attempt is made to set the object to null upon logging out. However, during compilation, the following error is thrown:

Error: src/app/auth/auth.service.ts:25:9 - error TS2322: Type 'null' is not assignable to type 'User'.

25         this.user = null;

I am currently following a course on Udemy, so the code should be correct according to that.

This is the interface of my User:

export interface User {
    email: string;
    userId: string;
}

Why is this error occurring? What detail have I overlooked? How can I address this issue?

Answer №1

It is considered best practice to set the type of 'user' variable as private user: User | null; or private user?: string; in TypeScript when assigning a value of null to it. This allows for better handling of cases where 'user' may be null.

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