The issue persists with Ionic failing to properly clean up pages upon exiting them

Question

The issue persists with Ionic failing to properly clean up pages upon exiting them

My introduction to Ionic (TypeScript + Angular) came out of necessity at work, as I had never worked on mobile development before. This is a whole new experience for me.

I'm currently facing an issue that has me completely stumped. Let me walk you through the scenarios:

Scenario 1

UserA logs in with their credentials
UserA is directed to their profile page after logging in
UserA logs out

Scenario 2

UserB logs in with their credentials
UserB is redirected to the profile page after logging in (but sees UserA's profile information)

Considerations

I am using @ionic/storage to manage sessions and it doesn't seem to be a storage-related problem. After logging out, I checked await session.get('user') which returned undefined. Upon logging back in, await session.get('user') displayed the correct user (the one who just logged in).

What Could Be Going Wrong?

I suspect that Ionic is caching the page when a new user logs in, preventing the constructor and ngOnInit methods from being called again. As a result, the variables retain old user data, leading to incorrect information being displayed.

This seems like the root cause because the issue doesn't occur consistently. Sometimes everything renders correctly initially, but I'm unsure how to resolve this :/

Questions

Has anyone encountered this issue before? What steps did you take to address it?

Is there a way to instruct Ionic not to cache the page?

Can the previous content be forcibly destroyed after a router.navigate() to another page?

angular typescript ionic-framework

Answer 1

Answer №1

When using Ionic, pages are not destroyed by default - they are kept in the DOM to allow for navigation using the back and forward buttons. While vanilla Angular routing allows you to control this behavior with RouteReuseStrategy, ion-router-outlet does not offer the same flexibility. Instead, ion-router-outlet uses a stack to store navigation history and only triggers Ionic lifecycle hooks after a component is created. If you want to clear this stack, you can use navigateRoot() or switch to Angular's router-outlet and router.

In my opinion, this is a notable flaw that is not well-documented. There are many situations where keeping a rendered component in the DOM indefinitely may not be ideal and could potentially lead to significant performance issues.

Answer 2

When using Ionic, pages are not destroyed by default - they are kept in the DOM to allow for navigation using the back and forward buttons. While vanilla Angular routing allows you to control this behavior with RouteReuseStrategy, ion-router-outlet does not offer the same flexibility. Instead, ion-router-outlet uses a stack to store navigation history and only triggers Ionic lifecycle hooks after a component is created. If you want to clear this stack, you can use navigateRoot() or switch to Angular's router-outlet and router.

In my opinion, this is a notable flaw that is not well-documented. There are many situations where keeping a rendered component in the DOM indefinitely may not be ideal and could potentially lead to significant performance issues.

Answer 3

Answer №2

Encountering a similar problem with Ionic 4 Angular 8, I managed to resolve it by implementing the use of { replaceUrl: true } upon logout button click. Here's an example:

logout() {
    ...
    this.router.navigate(["login"], { replaceUrl: true });
}

Answer 4

Encountering a similar problem with Ionic 4 Angular 8, I managed to resolve it by implementing the use of { replaceUrl: true } upon logout button click. Here's an example:

logout() {
    ...
    this.router.navigate(["login"], { replaceUrl: true });
}

Answer 5

Answer №3

When using Ionic, you may encounter situations where pages are kept in the DOM for transition and state purposes. To address this issue, Ionic provides lifecycle methods that allow you to reset the page's state when it is reentered. The IonViewWillEnter method is triggered every time the user navigates to the page, regardless of whether it is already in the DOM or not. For more information on how to use these events, please refer to the documentation: https://ionicframework.com/docs/angular/lifecycle

Answer 6

When using Ionic, you may encounter situations where pages are kept in the DOM for transition and state purposes. To address this issue, Ionic provides lifecycle methods that allow you to reset the page's state when it is reentered. The IonViewWillEnter method is triggered every time the user navigates to the page, regardless of whether it is already in the DOM or not. For more information on how to use these events, please refer to the documentation: https://ionicframework.com/docs/angular/lifecycle

Answer 7

Answer №4

If you substitute

<ion-router-outlet></ion-router-outlet>

with

<router-outlet></router-outlet>

, the lifecycle hooks of Angular will be activated, allowing you to meet your requirements more easily. However, this approach may not be suitable for an Ionic project.

Alternatively, you can include a router event listener in the constructor and handle further implementation to a certain extent.

For example:

this.router.events.subscribe((event : NavigationEnd) => {
  ...
})

Second technique :

In Ionic, modules are referred to as "Pages." To create pages/modules, use ionic generate page pageName. This way, all Ionic lifecycle hooks like ionViewWillEnter, ionViewDidLeave, etc., will function properly. For the main page, you can create a layout page (dashboard, other modules) and an auth page for login/logout/forgot password, etc.

Simply copy/paste your code from ngOnInit to ionViewWillEnter to ensure it works correctly.

Note: Some Ionic Components' lifecycle hooks may not work as expected, so it is advisable to make maximum use of Pages.

Answer 8

If you substitute

<ion-router-outlet></ion-router-outlet>

with

<router-outlet></router-outlet>

, the lifecycle hooks of Angular will be activated, allowing you to meet your requirements more easily. However, this approach may not be suitable for an Ionic project.

Alternatively, you can include a router event listener in the constructor and handle further implementation to a certain extent.

For example:

this.router.events.subscribe((event : NavigationEnd) => {
  ...
})

Second technique :

In Ionic, modules are referred to as "Pages." To create pages/modules, use ionic generate page pageName. This way, all Ionic lifecycle hooks like ionViewWillEnter, ionViewDidLeave, etc., will function properly. For the main page, you can create a layout page (dashboard, other modules) and an auth page for login/logout/forgot password, etc.

Simply copy/paste your code from ngOnInit to ionViewWillEnter to ensure it works correctly.

Note: Some Ionic Components' lifecycle hooks may not work as expected, so it is advisable to make maximum use of Pages.

Answer 9

Answer №5

Dealing with a frustrating cache issue on my page.ts where I needed to continuously check if the user was logged in or out to determine whether to display their information or not using a boolean condition, resulting in constantly refreshing the page.

At times, the webpage would show an outdated cached view and prevent me from seeing the logs on my checker function.

The solution that worked for me was implementing ionViewDidLeave() along with a subject.

I am currently utilizing angular 12 & ionic 5.

Here is an excerpt of the problematic page code:

isLogged: boolean;
private unsubscribe = new Subject<void>();

ionViewDidLeave() {
    console.log('Destroyed')
    this.unsubscribe.next()
    this.unsubscribe.complete();
}

ionViewWillEnter() {
    this.setIsLogged();
}

setIsLogged(): void {
   this._userDataService.getUser().pipe(
     takeUntil(this.unsubscribe)
   ).subscribe(
     (user) => {
      this.isLogged = true;
     },
     error => {
      this.isLogged = false;
     });
}

Hopefully, this solution can assist someone else experiencing similar issues :)

Answer 10

Dealing with a frustrating cache issue on my page.ts where I needed to continuously check if the user was logged in or out to determine whether to display their information or not using a boolean condition, resulting in constantly refreshing the page.

At times, the webpage would show an outdated cached view and prevent me from seeing the logs on my checker function.

The solution that worked for me was implementing ionViewDidLeave() along with a subject.

I am currently utilizing angular 12 & ionic 5.

Here is an excerpt of the problematic page code:

isLogged: boolean;
private unsubscribe = new Subject<void>();

ionViewDidLeave() {
    console.log('Destroyed')
    this.unsubscribe.next()
    this.unsubscribe.complete();
}

ionViewWillEnter() {
    this.setIsLogged();
}

setIsLogged(): void {
   this._userDataService.getUser().pipe(
     takeUntil(this.unsubscribe)
   ).subscribe(
     (user) => {
      this.isLogged = true;
     },
     error => {
      this.isLogged = false;
     });
}

Hopefully, this solution can assist someone else experiencing similar issues :)

The issue persists with Ionic failing to properly clean up pages upon exiting them

Scenario 1

Scenario 2

Considerations

What Could Be Going Wrong?

Questions

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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