Struct AVAUPresetEvent

Source

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

Available on crate feature AVMusicEvents only.

Expand description

The event class representing a preset load and change on the AVMusicTrack’s destinationAudioUnit.

AVAUPresetEvents make it possible to schedule and/or automate preset changes on the audio unit that has been configured as the destination for the AVMusicTrack containing this event.

Implementations§

Source §

impl AVAUPresetEvent

Source

pub unsafe fn initWithScope_element_dictionary( this: Allocated<Self>, scope: u32, element: u32, preset_dictionary: &NSDictionary, ) -> Retained<Self>

Initialize the event with the scope, element, and dictionary for the preset.

Parameter scope: The audio unit scope for the parameter (see AudioUnitScope). This should always be set to Global.

Parameter element: The element index within the scope (see AudioUnitElement). This should usually be set to 0.

Parameter presetDictionary: An NSDictionary containing the preset. The audio unit will expect this to be a dictionary structured as an appropriate audio unit preset.

The dictionary passed to this initializer will be copied and is not editable once the event is created.

Source

pub unsafe fn scope(&self) -> u32

The audio unit scope for the parameter (see AudioUnitScope). This should always be set to Global.

Source

pub unsafe fn setScope(&self, scope: u32)

Setter for scope.

Source

pub unsafe fn element(&self) -> u32

The element index within the scope (see AudioUnitElement). This should usually be set to 0.

Source

pub unsafe fn setElement(&self, element: u32)

Setter for element.

Source

pub unsafe fn presetDictionary(&self) -> Retained<NSDictionary>

An NSDictionary containing the preset.

Source §

impl AVAUPresetEvent

Methods declared on superclass NSObject.

Source

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

Source

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

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`
    }
}