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Learn how to convert your Promise handling in Angular to work seamlessly with Observables to avoid null values. This blog provides step-by-step instructions and code examples.
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How to Change Your Promise to an Observable in Angular and RxJS

As developers, we often encounter situations where we have to manage asynchronous data flows in our applications. In Angular, Promises are a common way to handle asynchronous operations, but when working with reactive programming using RxJS, Observables are often preferred due to their flexibility and ability to manage data streams.

In this blog, we'll explore how to convert a Promise-based service into an Observable-based service, focusing on an issue related to obtaining the selected language in an Angular application. If you’ve faced the frustration of getting null values from a service, this guide is tailored for you!

The Initial Problem

You have a service that fetches the selected language for your application. However, when you try to use this selected language in your component, you encounter a null value instead. This typically occurs because the Promise hasn't resolved before it's accessed in your component.

Here's a snippet of your current service code:

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

The Solution: Switching to Observables

By converting your logic to use Observables, you will be able to react to changes in your data asynchronously and avoid common pitfalls like null values. Below are the steps to refactor your service and component.

Step 1: Setting the Language with Observables

Here’s an example of how you can implement setLang using Observables:

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

Step 2: Making the Language Observable

To maintain the state of the selected language, it's advantageous to use a BehaviorSubject. You would set this up at the top of your service:

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

Step 3: Creating Getters for Observables

You need to create a getter for your selected language, as follows:

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

Step 4: Updating Your Component

In your component, subscribe to the language Observable and use the async pipe in your template to handle the data seamlessly:

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

In your template, use the async pipe:

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

Conclusion

By transitioning from Promises to Observables in your Angular application, you can better manage asynchronous data flows and avoid issues such as null values. Observables provide a powerful way to handle multiple data streams and allow your applications to remain responsive.

Start implementing these changes today, and enjoy a more robust and maintainable codebase!