DITPendingCursorOperation
@interface DITPendingCursorOperation : NSObject
These objects are returned when using find
-like functionality on DITCollection
s.
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 DITDocument
s 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
DITDocument
s 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
DITMutableDocument
s so you can call update-related functions on them.Return Value
A dictionary mapping document IDs to lists of
DITUpdateResult
s 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 toobserve
. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
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 toobserve
. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
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 toobserve
. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
to be called when an update occurs.Declaration
Objective-C
- (nonnull DITLiveQuery *)observeWithNextSignal: (nonnull void (^)(NSArray<DITDocument *> *_Nonnull, DITLiveQueryEvent *_Nonnull, DittoSignalNextBlock _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 toobserve
. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
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, DittoSignalNextBlock _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 callsubscribe
with the relevant query. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
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 callsubscribe
with the relevant query. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
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 callsubscribe
with the relevant query. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
to be called when an update occurs.Declaration
Objective-C
- (nonnull DITLiveQuery *)observeLocalWithNextSignal: (nonnull void (^)(NSArray<DITDocument *> *_Nonnull, DITLiveQueryEvent *_Nonnull, DittoSignalNextBlock _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 callsubscribe
with the relevant query. The returnedDITLiveQuery
object must be kept in scope for as long as you want the providedeventHandler
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, DittoSignalNextBlock _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.