Struct CKOperationGroup

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pub struct CKOperationGroup { /* private fields */ }

Available on crate feature CKOperationGroup only.

Expand description

A mechanism for your app to group several operations at the granularity of a user action.

For example, when building a Calendar application, these things might warrant being their own operation groups:

an initial fetch of data from the server, consisting of many queries, fetchChanges, and fetch operations
doing an incremental fetch of data in response to a push notification
saving several records due to a user saving a calendar event

You associate CKOperationGroups with CKOperations by setting the CKOperation.groupproperty. Create a new CKOperationGroupinstance for each distinct user action.

Implementations§

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impl CKOperationGroup

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

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pub unsafe fn initWithCoder( this: Allocated<Self>, a_decoder: &NSCoder, ) -> Retained<Self>

§Safety

a_decoder possibly has further requirements.

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

This is an identifier unique to this CKOperationGroup

This value is chosen by the system, and will be unique to this instance of a CKOperationGroup.This identifier will be sent to Apple’s servers, and can be used to identify any server-side logging associated with this operation group.

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pub unsafe fn defaultConfiguration(&self) -> Retained<CKOperationConfiguration>

Available on crate feature CKOperation only.

This is the default configuration applied to operations in this operation group.

If an operation associated with this operation group has its own configuration, then any explicitly-set properties in that operation’s configuration will override these default configuration values. See the example in CKOperation.h

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pub unsafe fn setDefaultConfiguration( &self, default_configuration: Option<&CKOperationConfiguration>, )

Available on crate feature CKOperation only.

Setter for defaultConfiguration.

This is copied when set.

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

Describes the user action attributed to the operation group.

nameshould describe the type of work being done. Some examples: “Initial Fetch” “Incremental Fetch” “Saving User-Entered Record” This string will be sent to Apple servers to provide aggregate reporting for CKOperationGroups and therefore must not include personally identifying data.

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pub unsafe fn setName(&self, name: Option<&NSString>)

Setter for name.

This is copied when set.

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pub unsafe fn quantity(&self) -> NSUInteger

Describes an application-specific “number of elements” associated with the operation group.

quantityis intended to show the app-specific count of items contained within the operation group. It is your job to assign meaning to this value. For example, if an app created an operation group to save 3 calendar events the user had created, the app might want to set this to “3”. This value is not shown to your users, it’s meant to aid your development and debugging. This value will be reported in the CloudKit Dashboard’s log entries for all operations associated with this operation group.

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pub unsafe fn setQuantity(&self, quantity: NSUInteger)

Setter for quantity.

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pub unsafe fn expectedSendSize(&self) -> CKOperationGroupTransferSize

Estimated size of traffic being uploaded to the CloudKit Server

Inform the system how much data you plan on transferring. Obviously, these won’t be exact. Be as accurate as possible, but even an order-of-magnitude estimate is better than no value. The system will consult these values when scheduling discretionary network requests (see the description of CKOperationConfiguration.qualityOfService).Overestimating your workload means that an operation group issuing discretionary network requests may be delayed until network conditions are good. Underestimating your workload may cause the system to oversaturate a constrained connection, leading to network failures. You may update after the CKOperationGroupis created. If it is increased, then subsequent CKOperations associated with this operation group may be delayed until network conditions are good. Defaults to CKOperationGroupTransferSizeUnknown

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pub unsafe fn setExpectedSendSize( &self, expected_send_size: CKOperationGroupTransferSize, )

Setter for expectedSendSize.

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pub unsafe fn expectedReceiveSize(&self) -> CKOperationGroupTransferSize

Estimated size of traffic being downloaded from the CloudKit Server

Inform the system how much data you plan on transferring. Obviously, these won’t be exact. Be as accurate as possible, but even an order-of-magnitude estimate is better than no value. The system will consult these values when scheduling discretionary network requests (see the description of CKOperationConfiguration.qualityOfService).Overestimating your workload means that an operation group issuing discretionary network requests may be delayed until network conditions are good. Underestimating your workload may cause the system to oversaturate a constrained connection, leading to network failures. You may update after the CKOperationGroupis created. If it is increased, then subsequent CKOperations associated with this operation group may be delayed until network conditions are good. Defaults to CKOperationGroupTransferSizeUnknown

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pub unsafe fn setExpectedReceiveSize( &self, expected_receive_size: CKOperationGroupTransferSize, )

Setter for expectedReceiveSize.

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impl CKOperationGroup

Methods declared on superclass NSObject.

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pub unsafe fn new() -> 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.

§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`
    }
}