Metadata

Metadata allows you to attach arbitrary information to your queries and mutations. This is powerful for handling global side effects, such as showing error toasts or analytics, without coupling your UI widgets to specific logic.

Query Meta

You can attach a QueryMeta object to any query options.


QueryOptions(
  meta: QueryMeta(
    successMessage: 'Data loaded successfully',
    errorMessage: 'Failed to load daily stats',
    // Custom arbitrary data map
    extras: {'showToast': true, 'severity': 'info'},
  ),
)

Global Side Effects

The real power comes when combining metadata with QueryClientObserver. You can create a global observer that listens to all queries and reacts based on their metadata.


class GlobalFeedbackObserver extends QueryClientObserver {
  @override
  void onQueryError(Query query, Object error) {
    // Check if the query has an error message defined in meta
    final meta = query.options.meta;
    if (meta?.errorMessage != null) {
      showToast(meta!.errorMessage!);
    }
  }
}
 
// Register it at app startup
final client = QueryClient();
client.addObserver(GlobalFeedbackObserver());

Mutation Meta

Similarly, mutations support MutationMeta.


MutationOptions(
  meta: MutationMeta(
    successMessage: 'Item created!',
    triggerCriticalHandler: true,
  ),
)

Usage Example


MutationBuilder<Todo, String>(
  mutationFn: addTodo,
  options: MutationOptions(
    meta: const MutationMeta(
      successMessage: 'Todo added successfully',
    ),
  ),
  builder: (context, state, mutate) {
    // ...
  },
)

API Reference

QueryMeta Properties

Property	Type	Description
`successMessage`	`String?`	Optional message for success events.
`errorMessage`	`String?`	Optional message for error events.
`invalidateKeys`	`List<QueryKey>`	Keys to invalidate on success (handled by observers).
`refetchKeys`	`List<QueryKey>`	Keys to refetch on success (handled by observers).

MutationMeta Properties

Property	Type	Description
`successMessage`	`String?`	Optional message for success events.
`errorMessage`	`String?`	Optional message for error events.
`invalidateKeys`	`List<QueryKey>`	Keys to invalidate on success.