Struct CNDecision

Source

pub struct CNDecision { /* private fields */ }

Available on crate feature CNDecision only.

Expand description

Represents a decision to focus on a specific detectionID or detectionGroupID; optionally strong.

A strong decision keeps focus for as long as possible.

Implementations§

Source §

impl CNDecision

Source

pub unsafe fn initWithTime_detectionID_strong( this: Allocated<Self>, time: CMTime, detection_id: CNDetectionID, is_strong: bool, ) -> Retained<Self>

Available on crate features CNDetection and objc2-core-media only.

Make a decision to focus on the detection with the given detectionID. A strong decision keeps focus for as long as possible.

Source

pub unsafe fn initWithTime_detectionGroupID_strong( this: Allocated<Self>, time: CMTime, detection_group_id: CNDetectionGroupID, is_strong: bool, ) -> Retained<Self>

Available on crate features CNDetection and objc2-core-media only.

Make a decision to focus on the best among those detections with the same detectionGroupID. A strong decision keeps focus for as long as possible.

Source

pub unsafe fn time(&self) -> CMTime

Available on crate feature objc2-core-media only.

The first presentation time at which the subject should be in focus. The rack focus transition to the subject occurs prior to this time.

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pub unsafe fn detectionID(&self) -> CNDetectionID

Available on crate feature CNDetection only.

The detectionID of the detection to focus on if this is not a group decision.

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pub unsafe fn detectionGroupID(&self) -> CNDetectionGroupID

Available on crate feature CNDetection only.

The detectionGroupID of the detection to focus on if this is a group decision.

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pub unsafe fn isUserDecision(&self) -> bool

Whether this is a user-created decision, or a base decision.

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pub unsafe fn isGroupDecision(&self) -> bool

Whether this is a group decision or not.

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pub unsafe fn isStrongDecision(&self) -> bool

Whether this is a strong decision or not. A strong decision keeps focus for as long as possible.

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

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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`
    }
}