OnMutateCallback<P> typedef

OnMutateCallback<P> = FutureOr Function(P params)

Lifecycle hook called immediately prior to executing a mutation.

May return an arbitrary context object (such as a rollback snapshot or telemetry token) which is subsequently passed to OnSuccessCallback, OnErrorCallback, and OnSettledCallback. Any exception thrown inside onMutate is swallowed to ensure the mutation proceeds.

OnMutateCallback<String> onMutate = (id) {
  print('Deleting task $id');
  return {'startTime': DateTime.now()};
};

Implementation

typedef OnMutateCallback<P> = FutureOr<dynamic> Function(P params);