SolidJS•2mo ago

createResource signal isn't trigger if undefined or null

let fetcher: Signal<number | undefined> = createSignal(3)

let r = createResource(fetcher, async (v) => console.log(v))

fetcher[1](undefined) // doesn't log anything
fetcher[1](null) // doesn't log anything

let fetcher: Signal<number | undefined> = createSignal(3)

let r = createResource(fetcher, async (v) => console.log(v))

fetcher[1](undefined) // doesn't log anything
fetcher[1](null) // doesn't log anything

Sometimes I want resource to return undefined, when the underlying signal goes undefined. That's how I like it. Why is this forbidden?.. If I change undefined with true it triggers as I expect it. but undefined makes more sense here.

2 Replies

Brendonovich•2mo ago

that's just how createResource works, i think it's done so that you can return non-nullable values from fetcher and have them end up in the resource function, as opposed to just using a boolean

foolswisdom•2mo ago

Also in the docs https://docs.solidjs.com/reference/basic-reactivity/create-resource

fetchData will be called as soon as source has any value other than false, null, or undefined.

Feels like it could be better surfaced if also described not as part of a snippet

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createResource signal isn't trigger if undefined or null