Struct AVAudioRoutingArbiter

Source

pub struct AVAudioRoutingArbiter { /* private fields */ }

Available on crate feature AVAudioRoutingArbiter only.

Expand description

The interface to participate in audio routing arbitration.

Implementations§

Source §

pub unsafe fn sharedRoutingArbiter() -> Retained<AVAudioRoutingArbiter>

Returns the singleton AVAudioRoutingArbiter instance.

Source

pub unsafe fn beginArbitrationWithCategory_completionHandler( &self, category: AVAudioRoutingArbitrationCategory, handler: &DynBlock<dyn Fn(Bool, *mut NSError)>, )

Available on crate feature block2 only.

Begin routing arbitration to take ownership of nearby Bluetooth audio routes.

When an app wants to participate in automatic audio arbitration for the wireless headphones route, it has to begin arbitration specifying its arbitration session category. It provides the operating system time to arbitrate with other nearby Apple devices to obtain ownership of supported Bluetooth audio devices. Then upon completion of arbitration, the operating system will automatically determine whether to route audio to the nearby Bluetooth device. Once arbitration completes, the application is free to start running audio I/O. I/O will be started upon the app request even if the -beginArbitrationWithCategory:completionHandler: fails. This method should also be used whenever restarting audio I/O in order to allow the system to arbitrate for ownership of a Bluetooth device that may have been taken by another nearby Apple device during the time that I/O was stopped.

Parameter category: The category describes the general type of audio that the app plans to use.

Parameter handler: A client-supplied block called asynchronously when audio routing arbitration is completed. This completion handler takes the following parameters: defaultDeviceChanged Indicating that the system default audio device has been changed as a result of the arbitration operation. error An error object that indicates why the request failed, or nil if the request was successful.

Source

pub unsafe fn leaveArbitration(&self)

Stop participating in audio routing arbitration.

When an application has stopped using audio for the foreseeable future, it should notify the system. For example, in Voice over IP (VoIP) use cases, the application should call -leaveArbitration when the VoIP call has ended. This allows the system to make a better decision when other participating Apple devices would like to take ownership of a nearby Bluetooth device. Applications should not call this API in cases where audio is only momentarily paused.

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`
    }
}