How to do incremental writing for UIDocument in iCloud? - ios

Question

I have UIDocument in iCloud ubiquitous container and I need to append data to file while saving document. I override readFromURL:: and writeContents::::: method according UIDocument documentation:
-(BOOL) writeContents:(id)contents toURL:(NSURL*)url forSaveOperation:(UIDocumentSaveOperation)saveOperation originalContentsURL:(NSURL*)originalContentsURL error:(NSError *__autoreleasing *)outError
{
NSFileCoordinator* coordinator = [[NSFileCoordinator alloc] initWithFilePresenter:self];
NSError* error = nil;
[coordinator coordinateWritingItemAtURL:url options:0 error:&error byAccessor:^(NSURL *newURL) {
NSData* data = contents; //correct, non-empty NSData
///[data writeToFile:newURL :] works, but overwrite original file
NSOutputStream* stream =[[NSOutputStream alloc] initWithURL:newURL append:YES];
if (stream)
{
NSInteger written = [stream write:data.bytes maxLength:data.length];
if (written != data.length)
{
//failed here, written == -1
NSLog(#"Write data to UIDocument failed: %#, error: %#", newURL, stream.streamError);
}
}
else
{
NSLog(#"Write data to iCloudDocument failed: %#", newURL);
}
}];
if (error)
{
NSLog(#"Coordinated write failed %#, error: %#", url, error);
*outError = error;
}
return error == nil;
}
Accessor block has different newURL, for example:
url: file:///private/var/mobile/Library/Mobile%20Documents/XXXXXXX~com~test~test/test.doc
newURL: file:///private/var/mobile/Applications/5631D484-7661-4E9E-A342-B25297FC0E18/tmp/(A%20Document%20Being%20Saved%20By%20test%20)/test.doc.
[stream write::] failed, because newURL file dosn't exists and I can't append data, only create file with all document's content.
Document editing code:
NSURL* url = [self.containerURL URLByAppendingPathComponent:kCloudDocumentName];
MyDocument* document = [[MyDocument alloc] initWithFileURL:url];
[document openWithCompletionHandler:^(BOOL success) {
if (success)
{
//update some document data
[self updateData:document completion:nil];
[document closeWithCompletionHandler:^(BOOL success) {
//failed here!
}];
}
}];
MyDocument exists in ubiquitous container at url and document has Normal state.
How I can do incremental writing in this case? Whats wrong?

Answer 1

After changing data in your UIDocumnet you can use:
-[UIDocumnet saveToURL:UIDocumnet.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:nil];
Not sure, it's right or not but it works in my app. If it's wrong, correct me please somebody.
You may need to overwrite this method in your subclass of UIDocumnet:
- (id) contentsForType:(NSString *)typeName error:(NSError **)outError