Struct AVMIDINoteEvent

Source

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

Available on crate feature AVMusicEvents only.

Expand description

The event class representing MIDI note-on/off messages.

Parameter channel: The MIDI channel for the note. Range: 0-15.

Parameter key: The MIDI key number for the note. Range: 0-127.

Parameter velocity: The MIDI velocity for the note. Range: 0-127 (see discussion).

Parameter duration: The duration of this note event in AVMusicTimeStamp beats. Range: Any non-negative number.

The AVAudioSequencer will automatically send a MIDI note-off after the note duration has passed. To send an explicit note-off event, create an AVMIDINoteEvent with its velocity set to zero.

Implementations§

Source §

impl AVMIDINoteEvent

Source

pub unsafe fn initWithChannel_key_velocity_duration( this: Allocated<Self>, channel: u32, key_num: u32, velocity: u32, duration: AVMusicTimeStamp, ) -> Retained<Self>

Available on crate feature AVAudioTypes only.

Initialize the event with a MIDI channel, key number, velocity and duration.

Parameter channel: The MIDI channel. Range: 0-15.

Parameter key: The MIDI key number. Range: 0-127.

Parameter velocity: The MIDI velocity. Range: 0-127 with zero indicating a note-off event.

Parameter duration: The duration in beats for this note. Range: Any non-negative number.

Source

pub unsafe fn channel(&self) -> u32

The MIDI channel for the event. Range: 0-15.

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pub unsafe fn setChannel(&self, channel: u32)

Setter for channel.

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pub unsafe fn key(&self) -> u32

The MIDI key number for the event. Range: 0-127.

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pub unsafe fn setKey(&self, key: u32)

Setter for key.

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pub unsafe fn velocity(&self) -> u32

The MIDI velocity for the event. Range: 0-127.

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pub unsafe fn setVelocity(&self, velocity: u32)

Setter for velocity.

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pub unsafe fn duration(&self) -> AVMusicTimeStamp

Available on crate feature AVAudioTypes only.

The duration of the event in AVMusicTimeStamp beats. Range: Any non-negative number.

Source

pub unsafe fn setDuration(&self, duration: AVMusicTimeStamp)

Available on crate feature AVAudioTypes only.

Setter for duration.

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impl AVMIDINoteEvent

Methods declared on superclass NSObject.

Source

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

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

Methods from Deref<Target = NSObject>§

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

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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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`
    }
}