Trait NSFileProviderEnumerating 

pub unsafe trait NSFileProviderEnumerating: NSObjectProtocol {
    // Provided method
    unsafe fn enumeratorForContainerItemIdentifier_request_error(
        &self,
        container_item_identifier: &NSFileProviderItemIdentifier,
        request: &NSFileProviderRequest,
    ) -> Result<Retained<ProtocolObject<dyn NSFileProviderEnumerator>>, Retained<NSError>>
       where Self: Sized + Message { ... }
}

Available on crate feature NSFileProviderReplicatedExtension only.

Apple’s documentation

Provided Methods

unsafe fn enumeratorForContainerItemIdentifier_request_error( &self, container_item_identifier: &NSFileProviderItemIdentifier, request: &NSFileProviderRequest, ) -> Result<Retained<ProtocolObject<dyn NSFileProviderEnumerator>>, Retained<NSError>>

where Self: Sized + Message,

Available on crate features NSFileProviderEnumerating and NSFileProviderItem and NSFileProviderRequest only.

Create an enumerator for an item.

This method is called when the user lists the content of folder it never accessed before. This can happen either when using Finder or when listing the content of the directory from a Terminal (for instance using the ls command line tool). The system will use the enumerator to list the children of the directory by calling -[NSFileProviderEnumerator enumerateItemsForObserver:startingAtPage:] until nil is passed to -[NSFileProviderEnumerationObserver finishEnumeratingUpToPage:]. Once this has been called, the directory and its children should be included in the working set.

This is also used to subscribe to live updates for a single document.

The system will keep an enumerator open in the extension on directories that are presented to the user (for instance, in Finder), and on document on which an application has a NSFilePresenter. The provider can use the existence of that enumerator as a hint that the user is actively seeing / using the item in question, and prioritize the delivery of updates on the item or its children in the working set.

If returning nil, you must set the error out parameter.

Working set enumerator:

The working set enumerator is a special enumerator (NSFileProviderWorkingSetContainerItemIdentifier) the system uses to detect changes that should be synced to the disk and/or searchable in Spotlight. Because that enumerator is by definition used for change detection, the working set enumerator must implement -[NSFileProviderEnumerator enumerateChangesForObserver:fromSyncAnchor:] and -[NSFileProviderEnumerator currentSyncAnchorWithCompletionHandler:].

The system guarantees that it has a single consumer for the working set. This means there will never be two concurrent enumerations of the working set and will always do forward progress: the system will only ask for changes from the last requested sync anchor or the last returned sync anchor and the extension should be prepared for it.

The expiration of the sync anchor of the working set will cause a very expensive scan of all the items known by the system.

The system ingests the changes from the working set and applies the changes to the disk replicate and the spotlight index. Before ingesting the update for an item, the system will check if the enumeration of the item races against a call to createItemBasedOnTemplate, modifyItem, … that may affect the item. If a potential race is detected, the system will call itemForItemIdentifier in order to resolve the race.

If the provider exposes the key NSExtensionFileProviderAppliesChangesAtomically with value YES in its Info.plist, it is considered to apply the changes atomically, in which case the system does not need to check for potential races.

Execution time:

The system expects this call to complete quickly, it should build the object that will be used for enumeration and return it. The enumeration logic should happen when the system calls -[NSFileProviderEnumerator enumerateItemsForObserver:startingAtPage:] or -[NSFileProviderEnumerator enumerateChangesForObserver:fromSyncAnchor:].

Error cases:

If containerItemIdentifier is NSFileProviderTrashContainerItemIdentifier and the extension does not support trashing items, then it should fail the call with the NSFeatureUnsupportedError error code from the NSCocoaErrorDomain domain.

If the item requested containerItemIdentifier does not exist in the provider, the extension should fail with NSFileProviderErrorNoSuchItem. In that case, the system will consider the item has been deleted and attempt to delete the item from disk.

The extension can also report the NSFileProviderErrorNotAuthenticated, NSFileProviderErrorServerUnreachable in case the item cannot be fetched because of the current state of the system / domain. In that case, the system will present an appropriate error message and back off until the next time it is signalled.

Any other error, including crashes of the extension process, will be considered to be transient and will cause the enumeration to be retried.

Errors must be in one of the following domains: NSCocoaErrorDomain, NSFileProviderErrorDomain.

For errors which can not be represented using an existing error code in one of these domains, the extension should construct an NSError with domain NSCocoaErrorDomain and code NSXPCConnectionReplyInvalid. The extension should set the NSUnderlyingErrorKey in the NSError’s userInfo to the error which could not be represented.

Trait Implementations

impl ProtocolType for dyn NSFileProviderEnumerating

const NAME: &'static str = "NSFileProviderEnumerating"

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

fn protocol() -> Option<&'static AnyProtocol>

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

impl<T> ImplementedBy<T> for dyn NSFileProviderEnumerating

where T: ?Sized + Message + NSFileProviderEnumerating,

Implementations on Foreign Types

impl<T> NSFileProviderEnumerating for ProtocolObject<T>

where T: ?Sized + NSFileProviderEnumerating,

Implementors