Update a specific element within Angular framework

Question

Update a specific element within Angular framework

Just starting out with angular and facing a seemingly simple issue that I can't seem to solve despite trying various solutions found on SO. I have created a login component where upon submission, the user is redirected to their profile page. While I am able to successfully redirect the user, the navigation bar at the top does not auto-refresh as intended. My goal is to have the navigation bar show the "Logout" button instead of the "Login/Register" button once the user logs in. Here's how my code files are structured:

login-page.component.html

<form #loginForm="ngForm" (ngSubmit)="loginUser(loginForm)" id="loginForm" class="loginbackground">
<input ngModel #emailAddress="ngModel" type="text" autocomplete="off" placeholder="Email" id="emailAddress" name="emailAddress" />
<button type="submit" id="submit">LOGIN</button>

login-page.component.ts

@Output() refreshEvent = new EventEmitter<any>();
loginUser(event) {
// Validations. If successful, proceed

const formData = event.value;
this.auth.loginUser(formData);
  .subscribe(data => {
    localStorage.setItem('loggedUser', JSON.stringify(data.userdata));
    // Form submit action here
    if (data.userdata.resMsg === 'Login failed') {
      this.errorPopup = true;
      this.errorText = 'Email Address and Password do not match';
    } else {
      this.refreshEvent.emit();
      this.emailAvailable = true;
      this.showLogin = false;
      this.showRegister = false;
      this.router.navigateByUrl('/404', { skipLocationChange: true }).then(() =>
        this.router.navigate(['user-profile']));
    }
  });
});
}

Problem
The issue arises when the nav bar doesn't update automatically after login. Manually refreshing the page resolves the problem but that's not ideal. I need the nav bar to reflect changes upon user login without needing manual intervention.

What I've tried

I attempted to implement the solution suggested here, but it didn't work for me.
Despite using an event emitter as shown above, I couldn't get it to function properly.
I also experimented with reloading the entire page using ngOnInit() to refresh the navigation bar component, but it caused an infinite loop. This was obviously a workaround, but I explored it nonetheless.

Is there a more elegant and effective way to achieve the desired outcome?

javascript angular typescript angular-components

Answer 1

Answer №1

This is the method I used to solve the problem:

navigation.component.html

...
<li *ngIf="!authenticationService.checkLoginStatus()">
  ...
</li>
<li *ngIf="authenticationService.checkLoginStatus()">
  ...
</li>
...

navigation.component.ts

export class NavigationComponent implements OnInit {

  constructor(public authenticationService: AuthenticationService) {
  }
  ...

authentication.service.ts

export class AuthenticationService {
  ...
  public checkLoginStatus() {
    return this.getUserId() !== null;
  }
  ...

In the 'checkLoginStatus' method, the 'this.getUserId()' function is used to retrieve the token from localStorage.

Answer 2

This is the method I used to solve the problem:

navigation.component.html

...
<li *ngIf="!authenticationService.checkLoginStatus()">
  ...
</li>
<li *ngIf="authenticationService.checkLoginStatus()">
  ...
</li>
...

navigation.component.ts

export class NavigationComponent implements OnInit {

  constructor(public authenticationService: AuthenticationService) {
  }
  ...

authentication.service.ts

export class AuthenticationService {
  ...
  public checkLoginStatus() {
    return this.getUserId() !== null;
  }
  ...

In the 'checkLoginStatus' method, the 'this.getUserId()' function is used to retrieve the token from localStorage.

Answer 3

Answer №2

Dealing with user authentication in Angular requires utilizing common features of the framework to ensure smooth functionality. Here is a breakdown of the process and sample code snippets to guide you through:

Thought process:

Problem: Ensuring constant awareness of the user's login status.
Solution: Implementing a service to track the user's login state.

Problem: Dynamic navigation bar based on user authentication.
Solution: Utilizing the authentication service to conditionally display navigation items according to the user's login status.

Code level issues:
Identifying code hurdles that may impede further development dependent on authentication status.

I've outlined two steps for enhancing your code. The first step focuses on improving data flow and code quality, while the second step offers a more dynamic approach.

Step 1

Service
Establish a variable within the Authentication Service to monitor the user's login status:

private isUserLoggedIn: boolean = false;

Migrate all authentication logic into the Authentication Service. Assume control over the this.auth.loginUser(formData) function by calling it from the new service and integrating its content into the revised login function.
Convert the HTTP call for login from an observable to a promise using .toPromise(), given its single-response nature.

The revised login function interacting with the API should resemble this:

private apiLogin(formData): Promise<any> {
        // Place the authentication logic here (use the relevant code from this.auth.loginUser(formData))
        // Presume 'loginObservable' holds the response from 'this.auth.loginUser(formData)'
        return new Promise((resolve, reject) => {
            this.auth.loginUser(formData)
                .toPromise()
                .then(data => {                   
                    if (data.userdata.resMsg === 'Login failed') {
                        localStorage.removeItem('loggedUser');
                        this.isUserLoggedIn = false;
                        reject('Email Address and Password do not match');
                    } else {
                        localStorage.setItem('loggedUser', JSON.stringify(data.userdata));
                        this.isUserLoggedIn = true;
                        resolve();
                    }
                })
                .catch(error => {
                    this.isUserLoggedIn = false;
                    reject(error);
                });
        })
    }

Implement a check to verify user login through local storage for seamless login experience across sessions:

// Check user login status via local storage
    private isAlreadyLoggedIn(): boolean {
        return !!localStorage.getItem('loggedUser');
    }

Introduce a login function triggered upon click events, bridging the service-calling component:

public login(formData): Promise<any> {        
        if (this.isAlreadyLoggedIn) {
            return Promise.resolve();
        } else {
            return this.apiLogin(formData);
        }
}

Add a constructor to initialize user login status verification & expose a public method for external status tracking:

constructor() {
        this.isUserLoggedIn = this.isAlreadyLoggedIn()
}
public isLoggedIn(): boolean {
        return this.isUserLoggedIn;
}

Complete service integration as demonstrated above.

Login Component:
Tweak component behavior to redirect already logged-in users to profile pages. Ensure error handling for better user interaction.

@Component({
    selector: 'app-login'
})
export class LoginComponent implements OnInit {
    ...
}

... (Content too long, request timed out) ...

Answer 4

Dealing with user authentication in Angular requires utilizing common features of the framework to ensure smooth functionality. Here is a breakdown of the process and sample code snippets to guide you through:

Thought process:

Problem: Ensuring constant awareness of the user's login status.
Solution: Implementing a service to track the user's login state.

Problem: Dynamic navigation bar based on user authentication.
Solution: Utilizing the authentication service to conditionally display navigation items according to the user's login status.

Code level issues:
Identifying code hurdles that may impede further development dependent on authentication status.

I've outlined two steps for enhancing your code. The first step focuses on improving data flow and code quality, while the second step offers a more dynamic approach.

Step 1

Service
Establish a variable within the Authentication Service to monitor the user's login status:

private isUserLoggedIn: boolean = false;

Migrate all authentication logic into the Authentication Service. Assume control over the this.auth.loginUser(formData) function by calling it from the new service and integrating its content into the revised login function.
Convert the HTTP call for login from an observable to a promise using .toPromise(), given its single-response nature.

The revised login function interacting with the API should resemble this:

private apiLogin(formData): Promise<any> {
        // Place the authentication logic here (use the relevant code from this.auth.loginUser(formData))
        // Presume 'loginObservable' holds the response from 'this.auth.loginUser(formData)'
        return new Promise((resolve, reject) => {
            this.auth.loginUser(formData)
                .toPromise()
                .then(data => {                   
                    if (data.userdata.resMsg === 'Login failed') {
                        localStorage.removeItem('loggedUser');
                        this.isUserLoggedIn = false;
                        reject('Email Address and Password do not match');
                    } else {
                        localStorage.setItem('loggedUser', JSON.stringify(data.userdata));
                        this.isUserLoggedIn = true;
                        resolve();
                    }
                })
                .catch(error => {
                    this.isUserLoggedIn = false;
                    reject(error);
                });
        })
    }

Implement a check to verify user login through local storage for seamless login experience across sessions:

// Check user login status via local storage
    private isAlreadyLoggedIn(): boolean {
        return !!localStorage.getItem('loggedUser');
    }

Introduce a login function triggered upon click events, bridging the service-calling component:

public login(formData): Promise<any> {        
        if (this.isAlreadyLoggedIn) {
            return Promise.resolve();
        } else {
            return this.apiLogin(formData);
        }
}

Add a constructor to initialize user login status verification & expose a public method for external status tracking:

constructor() {
        this.isUserLoggedIn = this.isAlreadyLoggedIn()
}
public isLoggedIn(): boolean {
        return this.isUserLoggedIn;
}

Complete service integration as demonstrated above.

Login Component:
Tweak component behavior to redirect already logged-in users to profile pages. Ensure error handling for better user interaction.

@Component({
    selector: 'app-login'
})
export class LoginComponent implements OnInit {
    ...
}

... (Content too long, request timed out) ...

Update a specific element within Angular framework

Answer №1

Answer №2

Step 1

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