Struct LADomainStateCompanion

Source

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

Available on crate feature LADomainState only.

Expand description

Apple’s documentation

Implementations§

Source §

impl LADomainStateCompanion

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pub unsafe fn availableCompanionTypes(&self) -> Retained<NSSet<NSNumber>>

Indicates types of companions paired with the device. The elements are NSNumber-wrapped instances of ``LACompanionType.

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pub unsafe fn stateHash(&self) -> Option<Retained<NSData>>

Contains combined state hash data for all available companion types. . Returns nil if no companion devices are paired.

As long as database of paired companion devices doesn’t change, stateHash stays the same for the same set of availableCompanions.

If database of paired companion devices was modified, stateHash data will change. Nature of such database changes cannot be determined but comparing data of stateHash after different policy evaluation will reveal the fact database was changed between calls.

If you are interested in a state hash for a specific companion type you can use stateHashForCompanionType method.

Warning: Please note that the value returned by this property can change exceptionally between major OS versions even if the list of paired companions has not changed.

Source

pub unsafe fn stateHashForCompanionType( &self, companion_type: LACompanionType, ) -> Option<Retained<NSData>>

Available on crate feature LACompanionType only.

Returns state hash data for the given companion type.

If database of paired devices of the given type was modified state hash data will change. Nature of such database changes cannot be determined but comparing data of state hash after different policy evaluation will reveal the fact database was changed between calls.

Parameter companionType: The companion type for which state hash data should be returned.

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

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

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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.

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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`
    }
}