Struct BGHealthResearchTask

Source

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>

Source

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

Methods from Deref<Target = BGTask>§

Source

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:.

Source

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.

There is a limit to how long your app has to perform its background work, and your work may need to be interrupted if system conditions change. Assign a handler to this property to cancel any ongoing tasks, perform any needed cleanup, and then call setTaskCompletedWithSuccess: to signal completion to the system and allow your app to be suspended. This property is cleared after it is called by the system or when BGTask/setTaskCompletedWithSuccess: is called. This is to mitigate the impact of a retain cycle created by referencing the BGTask instance inside this block.

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

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.
Note: The manager sets the value expirationHandler to nil after the handler completes.
Warning: Not setting an expiration handler results in the system marking your task as complete and unsuccessful instead of sending a warning.

Source

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

Available on crate feature block2 only.

Setter for expirationHandler.

Source

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

Inform the background task scheduler that the task is complete.

Call this method as soon as the background work associated with this task is complete. The system provides your app with a limited amount of time to finish the task. If you do not call setTaskCompletedWithSuccess: on the task, the system continues to run in the background until all the available time is consumed, wasting battery power. The system suspends the app as soon as all background tasks are complete.

Parameters:
success: A Boolean indicating if the task completed successfully or not. If the task was unsuccessful, you may request the system to try again later by submitting a new task request to the scheduler before calling this method.
Important: If you don’t set an expiration handler, the system will mark your task as complete and unsuccessful instead of sending a warning.
Warning: Not calling BGTask/setTaskCompletedWithSuccess: before the time for the task expires may result in the system killing your app.

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>§

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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`
    }
}