SolidJS•2mo ago

Why can I return a function from onMount?

Quick question: I'm allowed to (as in "TypeScript allows me to") return a function from the function I declare inside onMount. The docs does not comment on this (https://docs.solidjs.com/reference/lifecycle/on-mount), so what does it do? When is the returned function run? Example:

    onMount(() => {
        const subscriptionID = props.plexer.subscribe(PLAYER_MOVE_EVENT, (event) => {
            if (
                event.playerID === props.backend.localPlayer.id
                && event.locationID === props.colonyLocation.locationID
            ) {
                setUserIsHere(true);
            }
        });

        return () => {
            props.plexer.unsubscribe(subscriptionID);
        }
    })

    onMount(() => {
        const subscriptionID = props.plexer.subscribe(PLAYER_MOVE_EVENT, (event) => {
            if (
                event.playerID === props.backend.localPlayer.id
                && event.locationID === props.colonyLocation.locationID
            ) {
                setUserIsHere(true);
            }
        });

        return () => {
            props.plexer.unsubscribe(subscriptionID);
        }
    })

10 Replies

REEEEE•2mo ago

Nothing

FexelitcheOP•2mo ago

Welp. It could be? https://github.com/solidjs/solid/pull/2323

REEEEE•2mo ago

You could add the onCleanup to your onMount? I'm not sure if this will be added tbh

FexelitcheOP•2mo ago

Is that a thing? I.e.:

onMount(() => {
   onCleanup(()=>{});
})

onMount(() => {
   onCleanup(()=>{});
})

It feels wrong for some reason

REEEEE•2mo ago

You can put onCleanup generally wherever

FexelitcheOP•2mo ago

Man. I thought I had an incling of how those tracking scopes where implemented. But not anymore. That's for sure

REEEEE•2mo ago

fun fact, you can also do effects within effects

FexelitcheOP•2mo ago

Now, that's illegal Or. At least should be. Sounds ripe for OOM and other crashes

REEEEE•2mo ago

Yeah probably, I haven't found a usecase for them but I'm pretty sure it's used in the wild by someone might even be used in solid-primitives somewhere

FexelitcheOP•2mo ago

People are so concerned with whether they could - they didn't stop to think on whether they should - Some guy. Probably from Jurassic Park

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Why can I return a function from onMount?