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Docs: Explain optional relations #1647

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Aug 29, 2023
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Docs: Explain optional relations #1647

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37dc584
Explain optional relations
mfbx9da4 Aug 18, 2023
69533a2
Update docs-website/docs/docs/Components.md
mfbx9da4 Aug 18, 2023
606d78e
Update docs-website/docs/docs/Components.md
mfbx9da4 Aug 18, 2023
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9 changes: 7 additions & 2 deletions docs-website/docs/docs/Components.md
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Expand Up @@ -93,6 +93,11 @@ const EnhancedComment = enhance(Comment)

**Note** again that we can also pass `Relation` objects directly for convenience, skipping `.observe()`

### Reactive optional relations

Suppose the comment author is optional. If the comment has no author, the `comment.author_id` must be null. If `comment.author_id` has a value, the author record it refers to must be stored in the database, otherwise `withObservables` will throw an error that the record was not found.
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### Reactive counters

Let's make a `<PostExcerpt>` component to display on a *list* of Posts, with only a brief summary of the contents and only the number of comments it has:
Expand Down Expand Up @@ -256,8 +261,8 @@ With the `switchMap` approach, you can do:
const enhance = withObservables(['post'], ({post}) => ({
post: post,
author: post.author,
contact: post.autor.observe().pipe(
switchMap(author => author ? autor.contact : of$(null))
contact: post.author.observe().pipe(
switchMap(author => author ? author.contact : of$(null))
)
}))
```
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