Angular CanDeactivate Guard – Everything You Need to Know

When it comes to building modern web applications, Angular is one of the most popular and powerful front-end frameworks. It provides a variety of features and tools to help developers create highly performant and user-friendly applications. One such feature is the CanDeactivate Guard, which allows developers to control the navigation of their application based on certain conditions or criteria.

In this article, we will explore the CanDeactivate Guard in Angular in detail. We will discuss what it is, how it works, and how it can be used effectively in your application development process.

What is the CanDeactivate Guard?

The CanDeactivate Guard is a feature in Angular that allows developers to control the navigation of their application based on certain conditions or criteria. It is called a guard because it guards the route navigation process and determines whether or not the user is allowed to navigate to a different route.

The CanDeactivate Guard can be used to prevent the user from leaving a particular page or component if certain conditions are not met. For example, you can use it to prevent the user from leaving a form page if they have not completed all the required fields.

The CanActivate Guard is similar to the CanDeactivate Guard, but instead of preventing the user from leaving a page, it prevents them from entering a page if certain conditions are not met.

How does the CanDeactivate Guard work?

The CanDeactivate Guard works by intercepting the route navigation process and checking whether or not the user is allowed to navigate to a different route. It does this by implementing the CanDeactivate interface, which requires the implementation of a single method called canDeactivate.

The canDeactivate method takes two parameters: the current route and the current state of the route. It also returns a boolean value indicating whether or not the user is allowed to navigate to a different route.

The CanDeactivate Guard can be used to check for various conditions or criteria. For example, you can use it to check whether or not the user has completed all the required fields in a form, whether or not the user has unsaved changes on a page, or whether or not the user has confirmed that they want to leave a page.

How to implement the CanDeactivate Guard?

The implementation of the CanDeactivate Guard involves the following steps:

  1. Create a CanDeactivate Guard service by running the following command:

    2. ng generate service can-deactivate-guard

  2. Implement the CanDeactivate interface in the CanDeactivate Guard service:

    3. import { Injectable } from '@angular/core';
    import { CanDeactivate } from '@angular/router';
    import { Observable } from 'rxjs';

    @Injectable({
    providedIn: 'root'
    })
    export class CanDeactivateGuard implements CanDeactivate {

    canDeactivate(
    component: any,
    currentRoute: ActivatedRouteSnapshot,
    currentState: RouterStateSnapshot,
    nextState?: RouterStateSnapshot
    ): Observable | Promise | boolean {
    return true;
    }
    }

  3. Add the CanDeactivate Guard to the route that needs to be guarded:

    4. import { NgModule } from '@angular/core';
    import { Routes, RouterModule } from '@angular/router';
    import { HomeComponent } from './home/home.component';
    import { FormComponent } from './form/form.component';
    import { CanDeactivateGuard } from './can-deactivate-guard.service';

    const routes: Routes = [
    { path: '', component: HomeComponent },
    {
    path: 'form',
    component: FormComponent,
    canDeactivate: [CanDeactivateGuard]
    }
    ];

    @NgModule({
    imports: [RouterModule.forRoot(routes)],
    exports: [RouterModule]
    })
    export class AppRoutingModule { }

FAQs

What is the difference between CanActivate and CanDeactivate Guard?

The CanActivate Guard and the CanDeactivate Guard are both used to control the navigation of an Angular application. The main difference between them is that the CanActivate Guard prevents the user from entering a route, while the CanDeactivate Guard prevents the user from leaving a route.

What are some common use cases for the CanDeactivate Guard?

The CanDeactivate Guard can be used in a variety of scenarios, such as preventing the user from leaving a form page if they have not completed all the required fields, preventing the user from navigating away from a page with unsaved changes, or prompting the user to confirm that they want to leave a page.

Can I use multiple CanDeactivate Guards on a single route?

Yes, you can use multiple CanDeactivate Guards on a single route. Simply add them to the canDeactivate property of the route as an array.

Can I use the CanDeactivate Guard with lazy-loaded modules?

Yes, you can use the CanDeactivate Guard with lazy-loaded modules. Simply add the CanDeactivate Guard to the canDeactivate property of the route in the lazy-loaded module.

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