DITPendingCursorOperation

@interface DITPendingCursorOperation : NSObject

These objects are returned when using find-like functionality on DITCollections.

They allow chaining of further query-related functions to do things like add a limit to the number of documents you want returned or specify how you want the documents to be sorted and ordered.

You can either call exec on the object to get an array of DITDocuments as an immediate return value, or you can establish either a live query or a subscription, which both work over time.

A live query, established by calling observe, will notify you every time there’s an update to a document that matches the query you provided in the preceding find-like call.

A subscription, established by calling subscribe, will act as a signal to other peers that the device connects to that you would like to receive updates from them about documents that match the query you provided in the preceding find-like call.

Calling observe will generate both a subscription and a live query at the same time.

If you’d like to only observe local changes then you can call observeLocal.

If you want to observe changes in such a way that you can signal when you’re ready for the live query to deliver a new update then you can call observeWithNextSignal or observeLocalWithNextSignal.

Update and remove functionality is also exposed through this object.

  • Limit the number of documents that get returned when querying a collection for matching documents.

    Declaration

    Objective-C

    - (nonnull DITPendingCursorOperation *)limit:(int)limit;

    Parameters

    limit

    The maximum number of documents that will be returned.

    Return Value

    A DITPendingCursorOperation that you can chain further function calls and then either get the matching documents immediately or get updates about them over time.

  • Offset the resulting set of matching documents.

    This is useful if you aren’t interested in the first N matching documents for one reason or another. For example, you might already have queried the collection and obtained the first 20 matching documents and so you might want to run the same query as you did previously but ignore the first 20 matching documents, and that is when you would use offset.

    Declaration

    Objective-C

    - (nonnull DITPendingCursorOperation *)offset:(uint)offset;

    Parameters

    offset

    The number of matching documents that you want the eventual resulting set of matching documents to be offset by (and thus not include).

    Return Value

    A DITPendingCursorOperation that you can chain further function calls and then either get the matching documents immediately or get updates about them over time.

  • Sort the documents that match the query provided in the preceding find-like function call.

    Declaration

    Objective-C

    - (nonnull DITPendingCursorOperation *)sort:(nonnull NSString *)query
                                      direction:(DITSortDirection)direction;

    Parameters

    query

    The query specifies the logic to be used when sorting the matching documents.

    direction

    Specify whether you want the sorting order to be ascending or descending.

    Return Value

    A DITPendingCursorOperation that you can chain further function calls and then either get the matching documents immediately or get updates about them over time.

  • Execute the query generated by the preceding function chaining and return the list of matching documents.

    Declaration

    Objective-C

    - (nonnull NSArray<DITDocument *> *)exec;

    Return Value

    A list of DITDocuments matching the query generated by the preceding function chaining.

  • Remove all documents that match the query generated by the preceding function chaining.

    Declaration

    Objective-C

    - (nonnull NSArray<DITDocumentID *> *)remove;

    Return Value

    A list containing the IDs of the documents that were removed.

  • Evict all documents that match the query generated by the preceding function chaining.

    Declaration

    Objective-C

    - (nonnull NSArray<DITDocumentID *> *)evict;

    Return Value

    A list containing the IDs of the documents that were evicted.

  • Update documents that match the query generated by the preceding function chaining.

    Declaration

    Objective-C

    - (nonnull NSDictionary<DITDocumentID *, NSArray<DITUpdateResult *> *> *)
        updateWithBlock:
            (nonnull void (^)(NSArray<DITMutableDocument *> *_Nonnull))block;

    Parameters

    block

    A block that gets called with all of the documents matching the query. The documents are DITMutableDocuments so you can call update-related functions on them.

    Return Value

    A dictionary mapping document IDs to lists of DITUpdateResults that describes the updates that were performed for each document.

  • Enables you to subscribe to changes that occur in a collection remotely.

    Having a subscription acts as a signal to other peers that you are interested in receiving updates when local or remote changes are made to documents that match the query generated by the chain of operations that precedes the call to subscribe.

    The returned DITSubscription object must be kept in scope for as long as you want to keep receiving updates.

    Declaration

    Objective-C

    - (nonnull DITSubscription *)subscribe;

    Return Value

    A DITSubscription object that must be kept in scope for as long as you want to keep receiving updates for documents that match the query specified in the preceding chain.

  • Enables you to subscribe to changes that occur in a collection locally and remotely.

    The eventHandler block will be called when local or remote changes are made to documents that match the query generated by the chain of operations that precedes the call to observe. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)observe:
        (nonnull void (^)(NSArray<DITDocument *> *_Nonnull,
                          DITLiveQueryEvent *_Nonnull))eventHandler;

    Parameters

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observe was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally and remotely.

    The eventHandler block will be called when local or remote changes are made to documents that match the query generated by the chain of operations that precedes the call to observe. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)
        observeWithDeliveryQueue:(nonnull dispatch_queue_t)dispatchQueue
                    eventHandler:
                        (nonnull void (^)(NSArray<DITDocument *> *_Nonnull,
                                          DITLiveQueryEvent *_Nonnull))eventHandler;

    Parameters

    dispatchQueue

    The dispatch queue that will be used to deliver live query updates. Defaults to the main queue.

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observe was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally and remotely, and to signal when you are ready for the live query to deliver the next event.

    The eventHandler block will be called when local or remote changes are made to documents that match the query generated by the chain of operations that precedes the call to observe. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)observeWithNextSignal:
        (nonnull void (^)(NSArray<DITDocument *> *_Nonnull,
                          DITLiveQueryEvent *_Nonnull,
                          DITSignalNextBlock _Nonnull))eventHandler;

    Parameters

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observe was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally and remotely, and to signal when you are ready for the live query to deliver the next event.

    The eventHandler block will be called when local or remote changes are made to documents that match the query generated by the chain of operations that precedes the call to observe. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)
        observeWithNextSignalAndDeliveryQueue:
            (nonnull dispatch_queue_t)dispatchQueue
                                 eventHandler:
                                     (nonnull void (^)(
                                         NSArray<DITDocument *> *_Nonnull,
                                         DITLiveQueryEvent *_Nonnull,
                                         DITSignalNextBlock _Nonnull))eventHandler;

    Parameters

    dispatchQueue

    The dispatch queue that will be used to deliver live query updates. Defaults to the main queue.

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observe was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally.

    This won’t subscribe to receive changes made remotely by others and so it will only fire updates when a local change is made. If you want to receive remotely performed updates as well then use observe or call subscribe with the relevant query. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)observeLocal:
        (nonnull void (^)(NSArray<DITDocument *> *_Nonnull,
                          DITLiveQueryEvent *_Nonnull))eventHandler;

    Parameters

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observeLocal was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally.

    This won’t subscribe to receive changes made remotely by others and so it will only fire updates when a local change is made. If you want to receive remotely performed updates as well then use observe or call subscribe with the relevant query. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)
        observeLocalWithDeliveryQueue:(nonnull dispatch_queue_t)dispatchQueue
                         eventHandler:(nonnull void (^)(
                                          NSArray<DITDocument *> *_Nonnull,
                                          DITLiveQueryEvent *_Nonnull))eventHandler;

    Parameters

    dispatchQueue

    The dispatch queue that will be used to deliver live query updates. Defaults to the main queue.

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observeLocalWithDeliveryQueue was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally and to signal when you are ready for the live query to deliver the next event.

    This won’t subscribe to receive changes made remotely by others and so it will only fire updates when a local change is made. If you want to receive remotely performed updates as well then use observe or call subscribe with the relevant query. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)observeLocalWithNextSignal:
        (nonnull void (^)(NSArray<DITDocument *> *_Nonnull,
                          DITLiveQueryEvent *_Nonnull,
                          DITSignalNextBlock _Nonnull))eventHandler;

    Parameters

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observeLocalWithNextSignal was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.

  • Enables you to subscribe to changes that occur in a collection locally and to signal when you are ready for the live query to deliver the next event.

    This won’t subscribe to receive changes made remotely by others and so it will only fire updates when a local change is made. If you want to receive remotely performed updates as well then use observe or call subscribe with the relevant query. The returned DITLiveQuery object must be kept in scope for as long as you want the provided eventHandler to be called when an update occurs.

    Declaration

    Objective-C

    - (nonnull DITLiveQuery *)
        observeLocalWithNextSignalAndDeliveryQueue:
            (nonnull dispatch_queue_t)dispatchQueue
                                      eventHandler:
                                          (nonnull void (^)(
                                              NSArray<DITDocument *> *_Nonnull,
                                              DITLiveQueryEvent *_Nonnull,
                                              DITSignalNextBlock _Nonnull))
                                              eventHandler;

    Parameters

    dispatchQueue

    The dispatch queue that will be used to deliver live query updates. Defaults to the main queue.

    eventHandler

    A block that will be called every time there is a transaction committed to the store that involves modifications to documents matching the query in the collection that observeLocalWithNextSignalAndDeliveryQueue was called on.

    Return Value

    A DITLiveQuery object that must be kept in scope for as long as you want to keep receiving updates.