On 2011 Aug 04, at 08:30, Kevin Perry wrote:
> What Ken said.
OK, I'm back. Had to fork my project since Block_copy()/release() is not
available in 10.5 SDK. But it works now. See code below.
> Also, it might be more convenient to use NSBlockOperation or
> -addOperationWithBlock so the function parameters (including the completion
> handler) are all captured correctly for you automatically. It's a lot more
> convenient than stashing things in an NSDictionary.
Thank you, for my next project. But in this project I've got a home-made main
operation queue which I wrote back in the 10.5 days.
> Finally, I misspoke about the application blocking…
That was fine; you were using the word "block" in a broader sense - not just as
in threads.
> Also, what I said about other applications blocking trying to get sole access
> to the file via file coordination is still true.
If more changes are known to be coming in a few seconds, I think they should
wait.
** One little surprise. After dequeueing the save operation, I kind of thought
that I could invoke the new synchronous saving method
saveToURL:::completionHandler:. However, this does not save and apparently
does not run the completion handler properly because I still get the
hanging/blocking in -[NSDocument performAsynchronousFileAccessUsingBlock:].
But if I invoke the old async -saveToURL:::error: method and invoke the
completion handler block "manually", it works fine. Here…
/*!
@brief Real saving method, invoked when a save operation is
dequeued to do the actual work.
*/
- (void)reallySaveToURL:(NSURL *)url
ofType:(NSString *)typeName
forSaveOperation:(NSSaveOperationType)saveOperation
completionHandler:(void (^)(NSError *errorOrNil))completionHandler {
[self prepareForSaveOperation:saveOperation] ;
#if 0
#warning Using fancy new async saveToURL::::. Doesn't work.
[super saveToURL:url
ofType:typeName
forSaveOperation:saveOperation
completionHandler:completionHandler] ;
// Still hangs even if the following is commented out.
Block_release(completionHandler) ;
#else
#warning Invoking completionHandler manually. This works.
NSError* error = nil ;
BOOL ok = [super saveToURL:url
ofType:typeName
forSaveOperation:saveOperation
error:&error] ;
completionHandler(error) ;
Block_release(completionHandler) ;
if (error && ok) {
NSLog(@"Internal Error 923-0284 %@", error) ;
}
#endif
}
/*!
@brief Override of new asynchronous saving method invoked by Cocoa
when running in Mac OS X 10.7 or later.
@details
* Case saveOperation maenQueue Cancellable? Action
* ---- ------------- --------- ------------ --------------------
* 1 not AIP X X Add to queue
* 2 AIP not busy X Add to (empty) queue
* 3 AIP busy Yes Cancel the Save
* 4 AIP busy No Add to (busy) queue
AIP = Auto Save In Place
X = don't care
*/
- (void)saveToURL:(NSURL *)url
ofType:(NSString *)typeName
forSaveOperation:(NSSaveOperationType)saveOperation
completionHandler:(void (^)(NSError *errorOrNil))completionHandler {
if (saveOperation == NSAutosaveInPlaceOperation) {
// Case 2, 3 or 4
if ([[[SSYOperationQueue maenQueue] operations] count] != 0) {
// Case 3 or 4 (busy)
if ([self autosavingIsImplicitlyCancellable]) {
// Case 3. Cancel the Save
completionHandler([NSError errorWithDomain:NSCocoaErrorDomain
code:NSUserCancelledError
userInfo:nil]) ;
/*DB?Line*/ NSLog(@"133955: Cancelling Save") ;
return ;
}
else {
// Case 4. Add to (busy) queue
}
}
else {
// Case 2. Add to (empty) queue
}
}
else {
// Case 1. Add to queue
}
// Note that we arrive here either in Case 1, 2 or 4.
// In Case 2, and maybe Case 1, instead of adding the save
// operation to our queue, we could invoke -reallySaveToURL::::
// synchronously. However we don't do that because the usual
// notification sent when work is done, which we need for
// housekeeping, would not be sent, and also it would be
// extra code and an extra branch which means more testing
// and bug possibilities.
<snip>
… Code here adds operation to my SSYOperationQueue, kind of a
… cheesy main operation queue which I wrote back in the Leopard days
… for this project. It also copies the completionHandler block…
[info setValue:Block_copy(completionHandler) forKey:kCompletionHandler] ;
… When operation is dequeued, it invokes reallySaveToURL::::.
</snip>
}
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