toLazySignal

Using toLazySignal(), you can save some requests or improve performance.

This function works almost like the original toSignal() from Angular core (and uses it), but the subscription will be created not instantly - only when the resulting signal is read for the first time.

It might be helpful if you use resulting signals inside the @if or @switch branches.

import { toLazySignal } from 'ngxtension/to-lazy-signal';

Usage

const additionalList = toLazySignal(this.additionalList$);

toLazySignal() has the same signature as toSignal() - it accepts the same arguments and returns the same result. You can use it as a drop-in replacement.

Same as toSignal(), this function should be either called in an injection context (constructor, fields initialization), or an injector should be provided.

Source observable will be unsubscribed on the injector’s end of life - in the case of a component, it’s the moment when the component is destroyed. In the case of a service without {providedIn: "root"} - when the component, which injected this service, is destroyed.

But if a signal was created (using toSignal() or toLazySignal()) in a service with {providedIn: "root"}, or in a root component (usually AppComponent), the subscription will never be terminated.
Sometimes it’s exactly what we want, but most of the time it’s not.

Memory Leaks

As a general rule, it’s better to avoid using toSignal and toLazySignal() in root services and the root component to avoid memory leaks.

But, of course, there are always exceptions, and there are legit cases when a subscription should live as long as the application is alive, and such eternal subscriptions are not memory leaks.