Struct LAEnvironmentMechanismCompanion

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

Available on crate features LAEnvironmentMechanism and LAEnvironmentMechanismCompanion only.

Expand description

Apple’s documentation

Implementations§

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impl LAEnvironmentMechanismCompanion

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pub unsafe fn type(&self) -> LACompanionType

Available on crate feature LACompanionType only.

Type of the companion.

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

Hash of the current companion pairing as returned by LAContext.domainState.companion.stateHash(for:) If no companion are paired for this companion type, stateHashproperty is nil.If at least one companion is paired for this companion type, stateHashis not niland it changes whenever the set of paired companions of this type is changed.

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impl LAEnvironmentMechanismCompanion

Methods declared on superclass LAEnvironmentMechanism.

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

Clients should only consume environment mechanisms..

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

The Clients should only consume environment mechanisms..

Methods from Deref<Target = LAEnvironmentMechanism>§

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pub unsafe fn isUsable(&self) -> bool

Whether the mechanism is available for use, i.e. whether the relevant preflight call of canEvaluatePolicywould succeed.

Warning: If isUsablereads NO,do not assume that it’s because of some particular reason. You should check properties of the subclass to determine why mechanism can’t be used.

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pub unsafe fn localizedName(&self) -> Retained<NSString>

The localized name of the authentication mechanism, e.g. “Touch ID”, “Face ID” etc.

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pub unsafe fn iconSystemName(&self) -> Retained<NSString>

Name of the SF Symbol representing this authentication mechanism.

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.

§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());

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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`
    }
}