Make sure to wait for the observable to provide a value before proceeding with any operations involving the variable

Issue with handling observables:

someObservable$.subscribe(response => this.ref = response);

if (this.ref) {
    // do something with this.ref value
}
ERROR: this.ref is undefined

How can I ensure that the code relying on this.ref only runs after the subscription has provided a value for it?

I suspect that timing plays a role here, as the database subscription may need some time to complete. When I attach the above code to a button click event, it only executes after several clicks. Using setTimeout to wait 5 seconds before running the code could be a solution, but I'm curious if there's an RXJS operator or another approach designed for this issue.

Thank you.

typescriptrxjsobservablesubscription

Answer №1

Suppose someObservable$ represents an observable for an HTTP request, it is advisable to relocate the code that depends on this.ref inside the subscription handler. Take a look at this example:

someObservable$.subscribe(response => {
    this.ref = response;
    // Perform any necessary tasks that rely on this.ref within this block.
});

The subscription handler gets triggered once a response is received from the HTTP request. At this point, you should carry out the required operations. If this.ref is a variable related to a template, then the template should handle updating the view automatically with the new value.

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