Struct BGHealthResearchTask

Source

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

Available on crate feature BGTask only.

Expand description

A task meant to perform processing on behalf of health research studies.

Health research tasks may only be used by applications entitled to perform studies and user’s have opted in to the relevant study. These apps must have the com.apple.developer.backgroundtasks.healthresearch entitlement.

Implementations§

Source §

impl BGHealthResearchTask

Methods declared on superclass BGTask.

Source

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

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

Methods from Deref<Target = BGTask>§

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

The string identifier of the task.

The identifier is the same as the one used to register the launch handler in BGTaskScheduler/registerForTaskWithIdentifier:usingQueue:launchHandler:.

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pub unsafe fn expirationHandler(&self) -> *mut DynBlock<dyn Fn()>

Available on crate feature block2 only.

A handler called shortly before the task’s background time expires.

The time allocated by the system for expiration handlers doesn’t vary with the number of background tasks. All expiration handlers must complete before the allocated time.

Not setting an expiration handler results in the system marking your task as complete and unsuccessful instead of sending a warning.

The manager sets the value expirationHandler to nil after the handler completes.

Parameters:
expirationHandler: The expiration handler takes no arguments and has no return value. Use the handler to cancel any ongoing work and to do any required cleanup in as short a time as possible.

The handler may be called before the background process uses the full amount of its allocated time.

Source

pub unsafe fn setExpirationHandler( &self, expiration_handler: Option<&DynBlock<dyn Fn()>>, )

Available on crate feature block2 only.

Setter for expirationHandler.

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pub unsafe fn setTaskCompletedWithSuccess(&self, success: bool)

Informs the background task scheduler that the task is complete.

Not calling BGTask/setTaskCompletedWithSuccess: before the time for the task expires may result in the system killing your app.

You can reschedule an unsuccessful required task.

Important: If you don’t set an expiration handler, the system will mark your task as complete and unsuccessful instead of sending a warning.
Parameters:
success: A Boolean indicating if the task completed successfully or not.

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());

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`
    }
}