events.md

Events

CDTDatastore uses NSNotificationCenter to raise events for changes in the system.

Threading

Events may be fired from any thread. If you're modifying the UI in response to events (e.g., reloading a UITableView), switch to the main thread as you'd usually do, for example using GCD:

dispatch_async(dispatch_get_main_queue(), ^{
    ...
});

Database changed - CDTDatastoreChangeNotification

Defined in:

• CDTDatastore.h, included in CloudantSync.h.

Registration example:

CDTDatastore *datastore = [...];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(dbChanged:)
                                             name:CDTDatastoreChangeNotification
                                           object:datastore];

Object can be nil or a CDTDatastore instance. In the latter case, only notifications for that datastore will be delivered to your listener.

Fired when:

• When a document in a datastore is modified (created, updated or deleted).

In the userInfo dictionary for creating, updating and deleting revisions:

• rev: the new revision of the document.
• winner: the current winning revision for the document.

For changes as a result of replication, a field is added to the userInfo dictionary:

• source: NSURL of remote database, if added due to replication.

For the -deleteDocumentById:error: method, which may delete multiple revisions, in addition to the delete notifications for each revision there is an addition notification. Its userInfo dictionary contains:

• deletedRevs: an array containing all the deleted revisions.

Listener example:

/**
 Notified that a document has been created/updated/deleted.

 This method acts on changes to documents with the ID `self.documentToWatch`.
 */
- (void) dbChanged: (NSNotification*)n {
    CDTDocumentRevision* rev = (n.userInfo)[@"rev"];

    NSString* docID = rev.docId;
    if (![docID isEqualToString:self.documentToWatch])
        return;

    if (rev.deleted) {
        // do something
    }

    NSDictionary *body = [rev documentAsDictionary];

    // Process the current document's content using the
    // body dictionary...
}