Struct AVAssetWriterInputMetadataAdaptor

Source

pub struct AVAssetWriterInputMetadataAdaptor { /* private fields */ }

Available on crate feature AVAssetWriterInput only.

Expand description

Apple’s documentation

Implementations§

Source §

pub unsafe fn assetWriterInputMetadataAdaptorWithAssetWriterInput( input: &AVAssetWriterInput, ) -> Retained<Self>

Creates a new timed metadata group adaptor to receive instances of AVTimedMetadataGroup for writing to the output file.

The instance of AVAssetWriterInput passed in to this method must have been created with a format hint indicating all possible combinations of identifier (or, alternatively, key and keySpace), dataType, and extendedLanguageTag that will be appended to the metadata adaptor. It is an error to append metadata items not represented in the input’s format hint.

This method throws an exception for any of the following reasons:

input is already attached to another instance of AVAssetWriterInputMetadataAdaptor
input’s asset writer has already started writing (progressed beyond AVAssetWriterStatusUnknown)
input’s asset writer does not carry a source format hint
input’s source format hint media subtype is not kCMMetadataFormatType_Boxed
Parameter input: An instance of AVAssetWriterInput to which the receiver should append groups of timed metadata. Only asset writer inputs that accept media data of type AVMediaTypeMetadata can be used to initialize a timed metadata group adaptor.
Returns: An instance of AVAssetWriterInputMetadataAdaptor.

Source

pub unsafe fn initWithAssetWriterInput( this: Allocated<Self>, input: &AVAssetWriterInput, ) -> Retained<Self>

Creates a new timed metadator group adaptor to receive instances of AVTimedMetadataGroup for writing to the output file.

The instance of AVAssetWriterInput passed in to this method must have been created with a format hint indicating all possible combinations of identifier (or, alternatively, key and keySpace), dataType, and extendedLanguageTag that will be appended to the metadata adaptor. It is an error to append metadata items not represented in the input’s format hint. For help creating a suitable format hint, see -[AVTimedMetadataGroup copyFormatDescription].

This method throws an exception for any of the following reasons:

input is already attached to another instance of AVAssetWriterInputMetadataAdaptor
input’s asset writer has already started writing (progressed beyond AVAssetWriterStatusUnknown)
input’s asset writer does not carry a source format hint
input’s source format hint media subtype is not kCMMetadataFormatType_Boxed
Parameter input: An instance of AVAssetWriterInput to which the receiver should append groups of timed metadata. Only asset writer inputs that accept media data of type AVMediaTypeMetadata can be used to initialize a timed metadata group adaptor.
Returns: An instance of AVAssetWriterInputMetadataAdaptor.

Source

pub unsafe fn assetWriterInput(&self) -> Retained<AVAssetWriterInput>

The asset writer input to which the receiver should append timed metadata groups.

Source

pub unsafe fn appendTimedMetadataGroup( &self, timed_metadata_group: &AVTimedMetadataGroup, ) -> bool

Available on crate feature AVTimedMetadataGroup only.

Appends a timed metadata group to the receiver.

The receiver will retain the AVTimedMetadataGroup until it is done with it, and then release it.

The timing of the metadata items in the output asset will correspond to the timeRange of the AVTimedMetadataGroup, regardless of the values of the time and duration properties of the individual items.

Before calling this method, you must ensure that the input that underlies the receiver is attached to an AVAssetWriter via a prior call to -addInput: and that -startWriting has been called on the asset writer. It is an error to invoke this method before starting a session (via -[AVAssetWriter startSessionAtSourceTime:]) or after ending a session (via -[AVAssetWriter endSessionAtSourceTime:]).

This method throws an exception if the attached asset writer input has not been added to an asset writer or -startWriting has not been called on that asset writer.

Parameter timedMetadataGroup: The AVTimedMetadataGroup to be appended.
Returns: A BOOL value indicating success of appending the timed metadata group. If a result of NO is returned, AVAssetWriter.error will contain more information about why apending the timed metadata group failed.

Methods from Deref<Target = NSObject>§

Source

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

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

Source

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());

Source

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.

Source

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`
    }
}