UIDocument closeWithCompletionHandler: completes immediately

Question

Documentation of closeWithCompletionHandler" says: "After the save operation concludes, the code in completionHandler is executed." However, in my app this code:

NSLog(@"closeWithCompletionHandler");
[self.document closeWithCompletionHandler:^(BOOL success) {
    if (success) {
        NSLog(@"completionHandler");
...

executes immediately (on iOS6.1):

2013-07-18 19:43:12.673 FooBar[819:907] closeWithCompletionHandler
2013-07-18 19:43:12.675 FooBar[819:907] completionHandler <-- look here
2013-07-18 19:43:16.234 FooBar[819:907] encoded

even though actual writing data to a file takes several seconds (I know that by tracking contentsForType:error:).

contentsForType:error: implementation looks like this:

- (id)contentsForType:(NSString *)typeName error:(NSError *__autoreleasing *)outError
{
    NSMutableDictionary* wrappers = [NSMutableDictionary dictionary];
    [self encodeObject:self.data toWrappers:wrappers preferredFilename:kDocumentDataPath];
    NSFileWrapper* fileWrapper = [[NSFileWrapper alloc] initDirectoryWithFileWrappers:wrappers];

    NSLog("encoded");

    return fileWrapper;
}

Please note encoding finishing long after completionHandler executes:

2013-07-18 19:43:12.675 FooBar[819:907] completionHandler
2013-07-18 19:43:16.234 FooBar[819:907] encoded <-- look here

Why is this so? How should I make sure that data is written out to file before proceeding?

Ben Coffman · Answer 1 · 2013-07-19T15:19:21.333

1

I believe you want to look for the value of success being true, so your code might look like such

"How should I make sure that data is written out to file before proceeding?"

completionHandler: A block with code to execute after the save-and-close operation concludes. The block returns no value and has one parameter: success YES if any save operation succeeds, otherwise NO.

http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIDocument_Class/UIDocument/UIDocument.html#//apple_ref/occ/instm/UIDocument/closeWithCompletionHandler:

Answer:

NSLog(@"closeWithCompletionHandler");
[self.document closeWithCompletionHandler:^(BOOL success) {
     if(success){   
         NSLog(@"completionHandler");
     }

"Why is this so?"

Any number of reasons, one could be because the write failed and it's rolling back, another could be additonal OS overhead that iOS does. Last could be you are simply reading the length of time wrong.

edited Jul 19 '13 at 15:19

answered Jul 18 '13 at 18:19

Ben Coffman

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Right, but I already checked this and it does return success == YES. – proxi Jul 19 '13 at 07:17
I updated my answer, hopefully it helps a little more. The short is, you need to give more details on what exactly you are getting with contentsForType:error: and what the data is you are writing to the iOS along with the code you are using. Without this one can only guess why the file time is taking longer than you expect. – Ben Coffman Jul 19 '13 at 15:24
Thank you. I know about success flag, I am checking it (updated my question to reflect it) and it's not a problem. The problem is that completionHandler is called almost immediately, while documentation clearly says "code to execute AFTER the save-and-close operation". I'm writing big image and the save operation is expected to take long, I just want to make sure I don't proceed before the data is written out. – proxi Jul 20 '13 at 19:33

UIDocument closeWithCompletionHandler: completes immediately

1 Answers1