Struct AVCaptureMetadataOutput 

pub struct AVCaptureMetadataOutput { /* private fields */ }

Available on crate features AVCaptureMetadataOutput and AVCaptureOutputBase only.

AVCaptureMetadataOutput is a concrete subclass of AVCaptureOutput that can be used to process metadata objects from an attached connection.

Instances of AVCaptureMetadataOutput emit arrays of AVMetadataObject instances (see AVMetadataObject.h), such as detected faces. Applications can access the metadata objects with the captureOutput:didOutputMetadataObjects:fromConnection: delegate method.

See also Apple’s documentation

Implementations

impl AVCaptureMetadataOutput

pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

pub unsafe fn new() -> Retained<Self>

pub unsafe fn setMetadataObjectsDelegate_queue( &self, objects_delegate: Option<&ProtocolObject<dyn AVCaptureMetadataOutputObjectsDelegate>>, objects_callback_queue: Option<&DispatchQueue>, )

Available on crate feature dispatch2 only.

Sets the receiver’s delegate that will accept metadata objects and dispatch queue on which the delegate will be called.

Parameter objectsDelegate: An object conforming to the AVCaptureMetadataOutputObjectsDelegate protocol that will receive metadata objects after they are captured.

Parameter objectsCallbackQueue: A dispatch queue on which all delegate methods will be called.

When new metadata objects are captured in the receiver’s connection, they will be vended to the delegate using the captureOutput:didOutputMetadataObjects:fromConnection: delegate method. All delegate methods will be called on the specified dispatch queue.

Clients that need to minimize the chances of metadata being dropped should specify a queue on which a sufficiently small amount of processing is performed along with receiving metadata objects.

A serial dispatch queue must be used to guarantee that metadata objects will be delivered in order. The objectsCallbackQueue parameter may not be NULL, except when setting the objectsDelegate to nil otherwise -setMetadataObjectsDelegate:queue: throws an NSInvalidArgumentException.

Safety

objects_callback_queue possibly has additional threading requirements.

pub unsafe fn metadataObjectsDelegate( &self, ) -> Option<Retained<ProtocolObject<dyn AVCaptureMetadataOutputObjectsDelegate>>>

The receiver’s delegate.

The value of this property is an object conforming to the AVCaptureMetadataOutputObjectsDelegate protocol that will receive metadata objects after they are captured. The delegate is set using the setMetadataObjectsDelegate:queue: method.

pub unsafe fn metadataObjectsCallbackQueue( &self, ) -> Option<Retained<DispatchQueue>>

Available on crate feature dispatch2 only.

The dispatch queue on which all metadata object delegate methods will be called.

The value of this property is a dispatch_queue_t. The queue is set using the setMetadataObjectsDelegate:queue: method.

pub unsafe fn availableMetadataObjectTypes( &self, ) -> Retained<NSArray<AVMetadataObjectType>>

Available on crate feature AVMetadataObject only.

Indicates the receiver’s supported metadata object types.

The value of this property is an NSArray of NSStrings corresponding to AVMetadataObjectType strings defined in AVMetadataObject.h – one for each metadata object type supported by the receiver. Available metadata object types are dependent on the capabilities of the AVCaptureInputPort to which this receiver’s AVCaptureConnection is connected. Clients may specify the types of objects they would like to process by calling setMetadataObjectTypes:. This property is key-value observable.

pub unsafe fn metadataObjectTypes( &self, ) -> Retained<NSArray<AVMetadataObjectType>>

Available on crate feature AVMetadataObject only.

Specifies the types of metadata objects that the receiver should present to the client.

AVCaptureMetadataOutput may detect and emit multiple metadata object types. For apps linked before iOS 7.0, the receiver defaults to capturing face metadata objects if supported (see -availableMetadataObjectTypes). For apps linked on or after iOS 7.0, the receiver captures no metadata objects by default. -setMetadataObjectTypes: throws an NSInvalidArgumentException if any elements in the array are not present in the -availableMetadataObjectTypes array.

If you’ve set your AVCaptureMetadataOutput’s connected input’s cinematicVideoCaptureEnabled property to YES, you must set your metadataObjectTypes property to requiredMetadataObjectTypesForCinematicVideoCapture or an NSInvalidArgumentException is thrown.

pub unsafe fn setMetadataObjectTypes( &self, metadata_object_types: Option<&NSArray<AVMetadataObjectType>>, )

Available on crate feature AVMetadataObject only.

Setter for metadataObjectTypes.

This is copied when set.

pub unsafe fn rectOfInterest(&self) -> CGRect

Available on crate feature objc2-core-foundation only.

Specifies a rectangle of interest for limiting the search area for visual metadata.

The value of this property is a CGRect that determines the receiver’s rectangle of interest for each frame of video. The rectangle’s origin is top left and is relative to the coordinate space of the device providing the metadata. Specifying a rectOfInterest may improve detection performance for certain types of metadata. The default value of this property is the value CGRectMake(0, 0, 1, 1). Metadata objects whose bounds do not intersect with the rectOfInterest will not be returned.

As of iOS 13, this property can be set without requiring a lengthy rebuild of the session in which video preview is disrupted.

pub unsafe fn setRectOfInterest(&self, rect_of_interest: CGRect)

Available on crate feature objc2-core-foundation only.

Setter for rectOfInterest.

pub unsafe fn requiredMetadataObjectTypesForCinematicVideoCapture( &self, ) -> Retained<NSArray<AVMetadataObjectType>>

Available on crate feature AVMetadataObject only.

The required metadata object types when Cinematic Video capture is enabled.

Since the Cinematic Video algorithm requires a particular set of metadata objects to function optimally, you must set your metadataObjectTypes property to this property’s returned value if you’ve set AVCaptureDeviceInput/cinematicVideoCaptureEnabled to true on the connected device input, otherwise an NSInvalidArgumentException is thrown.

Methods from Deref<Target = AVCaptureOutput>

pub unsafe fn connections(&self) -> Retained<NSArray<AVCaptureConnection>>

Available on crate feature AVCaptureSession only.

The connections that describe the flow of media data to the receiver from AVCaptureInputs.

The value of this property is an NSArray of AVCaptureConnection objects, each describing the mapping between the receiver and the AVCaptureInputPorts of one or more AVCaptureInputs.

pub unsafe fn connectionWithMediaType( &self, media_type: &AVMediaType, ) -> Option<Retained<AVCaptureConnection>>

Available on crate features AVCaptureSession and AVMediaFormat only.

Returns the first connection in the connections array with an inputPort of the specified mediaType.

Parameter mediaType: An AVMediaType constant from AVMediaFormat.h, e.g. AVMediaTypeVideo.

This convenience method returns the first AVCaptureConnection in the receiver’s connections array that has an AVCaptureInputPort of the specified mediaType. If no connection with the specified mediaType is found, nil is returned.

pub unsafe fn transformedMetadataObjectForMetadataObject_connection( &self, metadata_object: &AVMetadataObject, connection: &AVCaptureConnection, ) -> Option<Retained<AVMetadataObject>>

Available on crate features AVCaptureSession and AVMetadataObject only.

Converts an AVMetadataObject’s visual properties to the receiver’s coordinates.

Parameter metadataObject: An AVMetadataObject originating from the same AVCaptureInput as the receiver.

Parameter connection: The receiver’s connection whose AVCaptureInput matches that of the metadata object to be converted.

Returns: An AVMetadataObject whose properties are in output coordinates.

AVMetadataObject bounds may be expressed as a rect where {0,0} represents the top left of the picture area, and {1,1} represents the bottom right on an unrotated picture. Face metadata objects likewise express yaw and roll angles with respect to an unrotated picture. -transformedMetadataObjectForMetadataObject:connection: converts the visual properties in the coordinate space of the supplied AVMetadataObject to the coordinate space of the receiver. The conversion takes orientation, mirroring, and scaling into consideration. If the provided metadata object originates from an input source other than the preview layer’s, nil will be returned.

If an AVCaptureVideoDataOutput instance’s connection’s videoOrientation or videoMirrored properties are set to non-default values, the output applies the desired mirroring and orientation by physically rotating and or flipping sample buffers as they pass through it. AVCaptureStillImageOutput, on the other hand, does not physically rotate its buffers. It attaches an appropriate kCGImagePropertyOrientation number to captured still image buffers (see ImageIO/CGImageProperties.h) indicating how the image should be displayed on playback. Likewise, AVCaptureMovieFileOutput does not physically apply orientation/mirroring to its sample buffers – it uses a QuickTime track matrix to indicate how the buffers should be rotated and/or flipped on playback.

transformedMetadataObjectForMetadataObject:connection: alters the visual properties of the provided metadata object to match the physical rotation / mirroring of the sample buffers provided by the receiver through the indicated connection. I.e., for video data output, adjusted metadata object coordinates are rotated/mirrored. For still image and movie file output, they are not.

pub unsafe fn metadataOutputRectOfInterestForRect( &self, rect_in_output_coordinates: CGRect, ) -> CGRect

Available on crate feature objc2-core-foundation only.

Converts a rectangle in the receiver’s coordinate space to a rectangle of interest in the coordinate space of an AVCaptureMetadataOutput whose capture device is providing input to the receiver.

Parameter rectInOutputCoordinates: A CGRect in the receiver’s coordinates.

Returns: A CGRect in the coordinate space of the metadata output whose capture device is providing input to the receiver.

AVCaptureMetadataOutput rectOfInterest is expressed as a CGRect where {0,0} represents the top left of the picture area, and {1,1} represents the bottom right on an unrotated picture. This convenience method converts a rectangle in the coordinate space of the receiver to a rectangle of interest in the coordinate space of an AVCaptureMetadataOutput whose AVCaptureDevice is providing input to the receiver. The conversion takes orientation, mirroring, and scaling into consideration. See -transformedMetadataObjectForMetadataObject:connection: for a full discussion of how orientation and mirroring are applied to sample buffers passing through the output.

pub unsafe fn rectForMetadataOutputRectOfInterest( &self, rect_in_metadata_output_coordinates: CGRect, ) -> CGRect

Available on crate feature objc2-core-foundation only.

Converts a rectangle of interest in the coordinate space of an AVCaptureMetadataOutput whose capture device is providing input to the receiver to a rectangle in the receiver’s coordinates.

Parameter rectInMetadataOutputCoordinates: A CGRect in the coordinate space of the metadata output whose capture device is providing input to the receiver.

Returns: A CGRect in the receiver’s coordinates.

AVCaptureMetadataOutput rectOfInterest is expressed as a CGRect where {0,0} represents the top left of the picture area, and {1,1} represents the bottom right on an unrotated picture. This convenience method converts a rectangle in the coordinate space of an AVCaptureMetadataOutput whose AVCaptureDevice is providing input to the coordinate space of the receiver. The conversion takes orientation, mirroring, and scaling into consideration. See -transformedMetadataObjectForMetadataObject:connection: for a full discussion of how orientation and mirroring are applied to sample buffers passing through the output.

pub unsafe fn isDeferredStartSupported(&self) -> bool

A BOOL value that indicates whether the output supports deferred start.

You can only set the deferredStartEnabled property value to true if the output supports deferred start.

pub unsafe fn isDeferredStartEnabled(&self) -> bool

A BOOL value that indicates whether to defer starting this capture output.

When this value is true, the session does not prepare the output’s resources until some time after AVCaptureSession/startRunning returns. You can start the visual parts of your user interface (e.g. preview) prior to other parts (e.g. photo/movie capture, metadata output, etc..) to improve startup performance. Set this value to false for outputs that your app needs for startup, and true for the ones it does not need to start immediately. For example, an AVCaptureVideoDataOutput that you intend to use for displaying preview should set this value to false, so that the frames are available as soon as possible.

By default, for apps that are linked on or after iOS 26, this property value is true for AVCapturePhotoOutput and AVCaptureFileOutput subclasses if supported, and false otherwise. When set to true for AVCapturePhotoOutput, if you want to support multiple capture requests before running deferred start, set AVCapturePhotoOutput/responsiveCaptureEnabled to true on that output.

If deferredStartSupported is false, setting this property value to true results in the system throwing an NSInvalidArgumentException.

• Note: Set this value before calling AVCaptureSession/commitConfiguration as it requires a lengthy reconfiguration of the capture render pipeline.

pub unsafe fn setDeferredStartEnabled(&self, deferred_start_enabled: bool)

Setter for isDeferredStartEnabled.

Methods from Deref<Target = NSObject>

pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>

pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

Panics

May panic if the object is invalid (which may be the case for objects returned from unavailable init/new methods).

Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());

pub unsafe fn get_ivar<T>(&self, name: &str) -> &T

where T: Encode,

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

Safety

The object must have an instance variable with the given name, and it must be of type T.

See Ivar::load_ptr for details surrounding this.

pub fn downcast_ref<T>(&self) -> Option<&T>

where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}

Trait Implementations

impl AsRef<AVCaptureMetadataOutput> for AVCaptureMetadataOutput

fn as_ref(&self) -> &Self

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<AVCaptureOutput> for AVCaptureMetadataOutput

fn as_ref(&self) -> &AVCaptureOutput

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<AnyObject> for AVCaptureMetadataOutput

fn as_ref(&self) -> &AnyObject

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<NSObject> for AVCaptureMetadataOutput

fn as_ref(&self) -> &NSObject

Converts this type into a shared reference of the (usually inferred) input type.

impl Borrow<AVCaptureOutput> for AVCaptureMetadataOutput

fn borrow(&self) -> &AVCaptureOutput

Immutably borrows from an owned value.

impl Borrow<AnyObject> for AVCaptureMetadataOutput

fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value.

impl Borrow<NSObject> for AVCaptureMetadataOutput

fn borrow(&self) -> &NSObject

Immutably borrows from an owned value.

impl ClassType for AVCaptureMetadataOutput

const NAME: &'static str = "AVCaptureMetadataOutput"

The name of the Objective-C class that this type represents.

type Super = AVCaptureOutput

The superclass of this class.

type ThreadKind = <<AVCaptureMetadataOutput as ClassType>::Super as ClassType>::ThreadKind

Whether the type can be used from any thread, or from only the main thread.

fn class() -> &'static AnyClass

Get a reference to the Objective-C class that this type represents.

fn as_super(&self) -> &Self::Super

Get an immutable reference to the superclass.

impl Debug for AVCaptureMetadataOutput

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Deref for AVCaptureMetadataOutput

type Target = AVCaptureOutput

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl Hash for AVCaptureMetadataOutput

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Message for AVCaptureMetadataOutput

fn retain(&self) -> Retained<Self>

where Self: Sized,

Increment the reference count of the receiver.

impl NSObjectProtocol for AVCaptureMetadataOutput

fn isEqual(&self, other: Option<&AnyObject>) -> bool

where Self: Sized + Message,

Check whether the object is equal to an arbitrary other object.

fn hash(&self) -> usize

where Self: Sized + Message,

An integer that can be used as a table address in a hash table structure.

fn isKindOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of the class, or one of its subclasses.

fn is_kind_of<T>(&self) -> bool

where T: ClassType, Self: Sized + Message,

👎Deprecated: use isKindOfClass directly, or cast your objects with AnyObject::downcast_ref

Check if the object is an instance of the class type, or one of its subclasses.

fn isMemberOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of a specific class, without checking subclasses.

fn respondsToSelector(&self, aSelector: Sel) -> bool

where Self: Sized + Message,

Check whether the object implements or inherits a method with the given selector.

fn conformsToProtocol(&self, aProtocol: &AnyProtocol) -> bool

where Self: Sized + Message,

Check whether the object conforms to a given protocol.

fn description(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object.

fn debugDescription(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object to use when debugging.

fn isProxy(&self) -> bool

where Self: Sized + Message,

Check whether the receiver is a subclass of the NSProxy root class instead of the usual NSObject.

fn retainCount(&self) -> usize

where Self: Sized + Message,

The reference count of the object.

impl PartialEq for AVCaptureMetadataOutput

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl RefEncode for AVCaptureMetadataOutput

const ENCODING_REF: Encoding = <AVCaptureOutput as ::objc2::RefEncode>::ENCODING_REF

The Objective-C type-encoding for a reference of this type.

impl DowncastTarget for AVCaptureMetadataOutput

impl Eq for AVCaptureMetadataOutput