Struct BGProcessingTask

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

Available on crate feature BGTask only.

A time-consuming processing task that runs while the app is in the background.

Use processing tasks for long data updates, processing data, and app maintenance. Although processing tasks can run for minutes, the system can interrupt the process. Add an expiration handler by setting BGTask/expirationHandler for any required cleanup.

Executing processing tasks requires setting the processing <doc ://com.apple.documentation/documentation/bundleresources/information_property_list/uibackgroundmodes> capability. For information on setting this capability, see BGTaskScheduler.

Processing tasks run only when the device is idle. The system terminates any background processing tasks running when the user starts using the device. Background refresh tasks are not affected.

See also Apple’s documentation

Implementations

impl BGProcessingTask

Methods declared on superclass BGTask.

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

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

Methods from Deref<Target = BGTask>

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:.

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.

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

Available on crate feature block2 only.

Setter for expirationHandler.

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>

pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>

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());

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.

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`
    }
}

Trait Implementations

impl AsRef<AnyObject> for BGProcessingTask

fn as_ref(&self) -> &AnyObject

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<BGProcessingTask> for BGHealthResearchTask

fn as_ref(&self) -> &BGProcessingTask

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<BGProcessingTask> for BGProcessingTask

fn as_ref(&self) -> &Self

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<BGTask> for BGProcessingTask

fn as_ref(&self) -> &BGTask

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<NSObject> for BGProcessingTask

fn as_ref(&self) -> &NSObject

Converts this type into a shared reference of the (usually inferred) input type.

impl Borrow<AnyObject> for BGProcessingTask

fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value.

impl Borrow<BGProcessingTask> for BGHealthResearchTask

fn borrow(&self) -> &BGProcessingTask

Immutably borrows from an owned value.

impl Borrow<BGTask> for BGProcessingTask

fn borrow(&self) -> &BGTask

Immutably borrows from an owned value.

impl Borrow<NSObject> for BGProcessingTask

fn borrow(&self) -> &NSObject

Immutably borrows from an owned value.

impl ClassType for BGProcessingTask

const NAME: &'static str = "BGProcessingTask"

The name of the Objective-C class that this type represents.

type Super = BGTask

The superclass of this class.

type ThreadKind = <<BGProcessingTask as ClassType>::Super as ClassType>::ThreadKind

Whether the type can be used from any thread, or from only the main thread.

fn class() -> &'static AnyClass

Get a reference to the Objective-C class that this type represents.

fn as_super(&self) -> &Self::Super

Get an immutable reference to the superclass.

impl Debug for BGProcessingTask

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Deref for BGProcessingTask

type Target = BGTask

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl Hash for BGProcessingTask

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Message for BGProcessingTask

fn retain(&self) -> Retained<Self>

where Self: Sized,

Increment the reference count of the receiver.

impl NSObjectProtocol for BGProcessingTask

fn isEqual(&self, other: Option<&AnyObject>) -> bool

where Self: Sized + Message,

Check whether the object is equal to an arbitrary other object.

fn hash(&self) -> usize

where Self: Sized + Message,

An integer that can be used as a table address in a hash table structure.

fn isKindOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of the class, or one of its subclasses.

fn is_kind_of<T>(&self) -> bool

where T: ClassType, Self: Sized + Message,

👎Deprecated: use isKindOfClass directly, or cast your objects with AnyObject::downcast_ref

Check if the object is an instance of the class type, or one of its subclasses.

fn isMemberOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of a specific class, without checking subclasses.

fn respondsToSelector(&self, aSelector: Sel) -> bool

where Self: Sized + Message,

Check whether the object implements or inherits a method with the given selector.

fn conformsToProtocol(&self, aProtocol: &AnyProtocol) -> bool

where Self: Sized + Message,

Check whether the object conforms to a given protocol.

fn description(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object.

fn debugDescription(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object to use when debugging.

fn isProxy(&self) -> bool

where Self: Sized + Message,

Check whether the receiver is a subclass of the NSProxy root class instead of the usual NSObject.

fn retainCount(&self) -> usize

where Self: Sized + Message,

The reference count of the object.

impl PartialEq for BGProcessingTask

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl RefEncode for BGProcessingTask

const ENCODING_REF: Encoding = <BGTask as ::objc2::RefEncode>::ENCODING_REF

The Objective-C type-encoding for a reference of this type.

impl DowncastTarget for BGProcessingTask

impl Eq for BGProcessingTask