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This commit introduces a dedicated error code for queries that require results but none are available. PR Close #54103
23 lines
1.5 KiB
Markdown
23 lines
1.5 KiB
Markdown
@name Child query result is required but no value is available.
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@category runtime
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@shortDescription Required child query result was accessed before query results were calculated or query has no matches.
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@description
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Required child query (`contentChild.required` or `viewChild.required`) result was accessed before query results were calculated or query has no matches.
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This can happen in two distinct situations:
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* query results were accessed before a given query could collect results;
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* a query was executed but didn't match any nodes and has no results as a consequence.
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Content queries and view queries each calculate their results at different points in time:
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* `contentChild` results are available after a _host_ view (template where a directive declaring a query is used) is created;
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* `viewChild` results are available after a template of a component declaring a query is created.
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Accessing query results before they're available results in the error described on this page. Most notably, query results are _never_ available in a constructor of the component or directive declaring a query.
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## Fixing the error
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`contentChild` query results can be accessed in the `AfterContentChecked` lifecycle hook, or later.
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`viewChild` query results can be accessed in the `AfterViewChecked` lifecycle hook, or later.
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Make sure that a required query matches at least one node and has results at all. You can verify this by accessing query results in the lifecycle hooks listed above.
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