Fetch Data via HTTP Using RxJS Observables and toSignal
Using Angular's toSignal function with the HTTP client enables components to reactively fetch and display data from external services.
This approach simplifies code and handles undefined initial values, but note that toSignal immediately subscribes and makes the HTTP request when used. So, keep in mind if you're using it in a component or some root level service.
[00:00] One of the most common usages of the 2 signal function is combining it with the HTTP client provided by Angular and relying on RxJS observables. I have created the user HTTP service, which uses the HTTP client and provides a get users public method, which does a simple get [00:19] HTTP request and return some data from an external service that is typed with a user array, an object that includes ID number and name string, the same type as we've been using so far. So currently, our component injects the user's HTTP service and has [00:39] an observable that creates the HTTP get service whenever it's subscribed. Here we can see a list which uses the users. Observable using the async pipe. So what we can do right now is to create yet again a signal version [01:00] of the HTTP get request and what we're going to pass is this dot users, HTTP service dot get users and make a call. Now we are not going to need this one And Angular is throwing an error over here so we're going to replace the async [01:19] pipe with just the call to the signal function. So let's save it again. Let's reload our application and we can see that it works exactly the same. What is important about the signal function combined with h t p client is that a signal, as mentioned [01:39] before, always needs to have a value. But with the HTP, we can't guarantee that the value would be there. So what signal does is first, it will extend the value with undefined as said before but also, it would make a subscription immediately. So bear [01:59] in mind if you're using to signal whether you use it from within a component or a service, especially if the service is provided in root.