Cast from `Type | undefined`

Hi everyone. I'm trying to show a data from Sanity CMS, using createAsync:

const data = createAsync(() => getProject(params.slug));

const data = createAsync(() => getProject(params.slug));

But the problem is, any way to cast dat() to my Type removing the Type | undefined? Because currently the ProjectHeroSection is complain because the data() could be undefined, but at this point I know that isn't undefined.

<Show when={!!data()}>
      <ProjectHeroSection
        title={data()?.title}
        headline={data()?.headline}
        thumbnail={data()?.thumbnail}
      />
</Show>

<Show when={!!data()}>
      <ProjectHeroSection
        title={data()?.title}
        headline={data()?.headline}
        thumbnail={data()?.thumbnail}
      />
</Show>

Anyone can help me please?

6 Replies

Brendan•4mo ago

This is sort of just normal really. Typescript has no way to know that your Show component means that other calls to data() will always have a value. Since you know better, you can assert the value is non-null if you want to (with ! instead of ?):

      <ProjectHeroSection
        title={data()!.title}a
        headline={data()!.headline}
        thumbnail={data()!.thumbnail}
      />

      <ProjectHeroSection
        title={data()!.title}a
        headline={data()!.headline}
        thumbnail={data()!.thumbnail}
      />

Daniel Sousa @TutoDS•4mo ago

but any way to assert the value to non-null for the entire component (inside the Show)?

Madaxen86•4mo ago

Sure. Show provides also a callback for children which provides the value of the truthy when condition. So you should remove the double “!!“:

<Show when={data()}>
      {(post) => <ProjectHeroSection
        title={post().title}
        headline={post().headline}
               thumbnail={post().thumbnail}
      />
</Show>

<Show when={data()}>
      {(post) => <ProjectHeroSection
        title={post().title}
        headline={post().headline}
               thumbnail={post().thumbnail}
      />
</Show>

There’s also a keyed prop for show which turns the callback value into a store like object. See last example in the docs: https://docs.solidjs.com/reference/components/show

Daniel Sousa @TutoDS•4mo ago

Thanks and sorry for the noob questions

Madaxen86•4mo ago

Your welcome. No need to be sorry ☺️

Daniel Sousa @TutoDS•4mo ago

~~For some reason, the value on the callback isn't a accessor but the value itself~~ Sorry, now I understand the usage of keyed property

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Cast from `Type | undefined`