Скачать или смотреть Solving the async Function Return Type Issue in Angular Route Guards

Learn how to address the error regarding the return type of an async function in Angular route guards. This guide provides a clear solution with examples for better understanding.
---
This video is based on the question https://stackoverflow.com/q/63540828/ asked by the user 'alvardo' ( https://stackoverflow.com/u/2562133/ ) and on the answer https://stackoverflow.com/a/63541391/ provided by the user 'Rafi Henig' ( https://stackoverflow.com/u/9369606/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: The return type of an async function or method must be the global Promise T type Angular

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Solving the async Function Return Type Issue in Angular Route Guards

When working with Angular applications, it's common to encounter issues regarding the return type of asynchronous functions, particularly when implementing route guards. One common error developers face is the complaint that "The return type of an async function or method must be the global Promise type." In this guide, we'll explore this problem and provide a well-structured solution to overcome it.

Understanding the Problem

As developers, we often need to control user access to different routes in our application based on business logic. Route guards are a powerful feature in Angular that allow us to implement this logic effectively. However, if we specify an incorrect return type in our guard's canActivate method, Angular will throw an error.

The Error

Here's a snippet of the initial guard implementation you might be using:

[[See Video to Reveal this Text or Code Snippet]]

Here, the use of async along with returning an Observable can lead to inconsistency and confusion for Angular.

Solution Overview

To solve this issue, we should ensure the guard's return type matches what Angular expects. The solution is to return an Observable rather than converting results to Promises.

Adjusting the Return Type

Remove the async Keyword: The async keyword is not needed when you are returning an Observable.

Use combineLatest: This operator allows us to work with multiple Observables simultaneously, making our code cleaner and more efficient.

Revised Code Example

Here's how you can implement the changes:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Revised Code

1. Removed async: By getting rid of the async modifier, we maintain the type consistency with Angular expectations.

2. Using combineLatest: This function is combined with the result of this.authService.getUserSubject() and this.clienteService.obtenerCliente(idCliente), allowing us to subscribe to both Observables for real-time changes.

3. Using pipe and map: The pipe function helps us chain RxJS operators, and map takes the results from both Observables to check if the user is allowed to navigate.

Conclusion

By understanding the return type requirements of Angular's async functions and utilizing Observables effectively, you can create route guards that work smoothly without throwing errors. Make sure to follow the structure we discussed, particularly with the use of combineLatest, to streamline your route guarding processes in Angular applications.

With this knowledge in hand, you should be well-equipped to tackle similar issues in your projects. Happy coding!