Instance Method

setMetadataObjectsDelegate:queue:

Sets the delegate and dispatch queue to use handle callbacks.

Declaration

- (void)setMetadataObjectsDelegate:(id<AVCaptureMetadataOutputObjectsDelegate>)objectsDelegate queue:(dispatch_queue_t)objectsCallbackQueue;

Parameters

objectsDelegate

The delegate object to notify when new metadata objects become available. This object must conform to the AVCaptureMetadataOutputObjectsDelegate protocol.

objectsCallbackQueue

The dispatch queue on which to execute the delegate’s methods. This queue must be a serial queue to ensure that metadata objects are delivered in the order in which they were received. If the objectsDelegate parameter is nil, you may specify nil for this parameter too; otherwise, you must specify a valid dispatch queue.

Discussion

When new metadata objects are captured from the receiver’s connection, they are vended to the delegate object. All delegate methods are executed on the dispatch queue specified in the objectsCallbackQueue parameter. To ensure that metadata objects are processed in a timely manner and not dropped, you should specify a dispatch queue dedicated to processing the objects or that is otherwise not busy.

See Also

Receiving Captured Metadata Objects

metadataObjectsDelegate

The delegate of the capture metadata output object.

metadataObjectsCallbackQueue

The dispatch queue on which to execute the delegate’s methods.

AVCaptureMetadataOutputObjectsDelegate

Methods for receiving metadata produced by a metadata capture output.