Understanding the 'CanDeactivate' Guard in Angular Routing

In Angular, the 'CanDeactivate' guard is used to confirm navigation away from the current route. This is particularly useful when you need to ensure that users do not mistakenly leave a form or a process that they are currently engaged with.

The 'CanDeactivate' guard can confirm navigation away from a route by running some logic when a user attempts to leave the page. If the guard returns "true", the navigation will proceed. If it returns "false", the navigation process is halted and the user remains on the current page.

Practical Application of 'CanDeactivate' Guard

Consider a scenario where a user is filling out a long form on your web application. If they accidentally navigate away (perhaps by clicking a link or if their internet connection is lost), all their progress would be lost, which could potentially frustrate the user. In this case, the 'CanDeactivate' guard comes to the rescue.

With 'CanDeactivate' guard, you can show a confirmation dialog to the user and ask if they really want to leave their current page. This way, you can prevent them from losing their filled out data accidentally.

Here's how you would generally use it:

canDeactivate(
  component: ComponentCanDeactivate,
  currentRoute: ActivatedRouteSnapshot,
  currentState: RouterStateSnapshot,
  nextState?: RouterStateSnapshot): Observable<boolean>|Promise<boolean>|boolean {

  return component.canDeactivate();
}

In this code, component.canDeactivate() would return either a boolean or an Observable or Promise that resolves to a boolean. This boolean value decides if the navigation can proceed (true) or not (false).

Best Practices and Additional Insights

• Do not solely rely on 'CanDeactivate' guard for data protection. It does not 100% guarantee against data loss, for instance, if the user unexpectedly closes their browser. Therefore, as a best practice, also use mechanisms like auto-save to ensure data persistence.

• Carefully consider where to apply the 'CanDeactivate' guard. Constant confirmation dialogues can annoy or unnerve users. Use them only when it’s absolutely necessary to protect important user data or changes.

In conclusion, the 'CanDeactivate' guard is a powerful tool in Angular that ensures better user experience by confirming navigation away from the current route. It empowers developers to build more interactive and user-friendly applications - just remember to use it judiciously and wisely.