Struct AVAssetWriterInputCaptionAdaptor

Source

#[repr(C)]
pub struct AVAssetWriterInputCaptionAdaptor { /* private fields */ }

Available on crate feature AVAssetWriterInput only.

Expand description

An adaptor class for appending instances of AVCaption to an asset writer input. -[AVAssetWriterInput -appendSampleBuffer:] will throw an exception if used when this adaptor is attached.

Implementations§

Source §

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

Creates a new caption adaptor for writing to the specified asset writer input.

Source

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

Creates a new caption adaptor for writing to the specified asset writer input.

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

input is nil
the input’s media type is not supported (should use text or closed caption)
the input is already attached to an asset writer caption adaptor
the input has already started writing

Source

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

The asset writer input that was used to initialize the receiver.

Source

pub unsafe fn appendCaption(&self, caption: &AVCaption) -> bool

Available on crate feature AVCaption only.

Append a single caption to be written.

Parameter caption: The caption to append.

Returns: Returns YES if the operation succeeded, NO if it failed.

If this method returns NO, check the value of AVAssetWriter.status on the attached asset writer to determine why appending failed.

The start time of each caption’s timeRange property must be numeric (see CMTIME_IS_NUMERIC) and must be at least as large as the start time of any previous caption (including any captions present in a group appended via -appendCaptionGroup:). In other words, the sequence of captions appended using this method must have monotonically increasing start times.

The duration of each caption’s timeRange property must be numeric.

Source

pub unsafe fn appendCaptionGroup(&self, caption_group: &AVCaptionGroup) -> bool

Available on crate feature AVCaptionGroup only.

Append a group of captions to be written.

Parameter captionGroup: Returns: Returns YES if the operation succeeded, NO if it failed.

If this method returns NO, check the value of AVAssetWriter.status on the attached asset writer to determine why appending failed. When appending a sequence of captions groups, the start time of each group must be equal to or greater than the end time of any previous group. The easiest way to achieve this is to create the group using a caption whose duration is kCMTimeInvalid, in which case the duration will be determined by subtracting the start time of the group from the start time of the next appended group. When mixing calls to -appendCaptionGroup: and -appendCaption:, the start time of each group must be equal to or greater than the end time of any previous captions. To mark a time range containing no captions, append a group containing an empty caption array.

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.

§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`
    }
}