I am making minor edits to a QTMovie in an application using NSDocument architecture (such as adding a track, as shown below). After the edit, I want to save to the original file. However, I keep getting a 'file is busy' error. I assume this is due to some oversight I made in the handling of the files, or a failure in how I am using NSDocument. Any tips would be helpful! Here is (some of) the relevant code:
// open file that has the track I want to add to my movie
QTMovie* tempMovie = [QTMovie movieWithURL:outputFileURL error:nil];
// Use old API to add the track
AddMovieSelection([movie quickTimeMovie], [tempMovie quickTimeMovie]);
// get the filename from the NSDocument
NSString *filename = [[self fileURL] path];
NSLog(#"writing to filename: %#", filename);
// FLATTEN the movie file so I don't get external references
NSMutableDictionary *attributes = [NSMutableDictionary dictionaryWithCapacity:1];
[attributes setObject:[NSNumber numberWithBool:YES] forKey:QTMovieFlatten];
// attempt to write
NSError *error;
// this is where I get the "file is busy"
if (![movie writeToFile:filename withAttributes:attributes error:&error]) {
NSLog(#"Error: %#", [error localizedDescription]);
NSRunAlertPanel(#"Error", [error localizedDescription], nil, nil, nil);
}
Do I have to first release the movie in my NSDocument? What is the "proper" way to do that? Keep in mind, I am not necessarily finished with this document, I am not closing it. I have just finished this operation, and I want the file on disk to reflect my changes. I would love to use [movie updateMovieFile], but that call doesn't seem to flatten the movie. I don't want any external references in my file.
I am not too familiar with the QuickTime C API, so I honestly can't tell you anything about what is going wrong there. Absolute guesswork: Maybe a call to EndMediaEdits is missing?
Though that shouldn't be required by AddMovieSelection, you said "[...] such as adding a track [...]". So maybe there is something else going on, like AddMediaSample or something similar?
That said, if you don't need to target anything below 10.5 and all you need to do is add some segment from another movie, you can achieve that without dropping down to the C API:
Have a look at
-[QTMovie insertSegmentOfTrack:fromRange:scaledToRange:]
and
-[QTMovie insertSegmentOfMovie:fromRange:scaledToRange:], if you want to have the inserted segment "overlayed" (temporally speaking).
-[QTMovie insertSegmentOfMovie:timeRange:atTime:] and -[QTMovie insertSegmentOfTrack:timeRange:atTime:], if you want { movieA.firstPart, movieB, movieA.secondPart }.
Do I have to first release the movie in my NSDocument?
You mean in order to write it to disk? No: That should even result in a crash.
The role of release is to handle memory-management. It doesn't have much to do with the busy-state of a file.
Turns out I just wasn't using the NSDocument architecture properly. When I changed it to use Save/SaveAs properly, this problem went away.
Related
When I Analyze a class I'm working on this line of code:
myObject.myImageData = [NSData dataWithContentsOfURL:[[NSURL alloc] initWithString:myObject.thumbnailUrlString]];
has a warning Potential leak of an object.
Any idea why and how you fix it?
==== Note
If I try and separate this line out I get additional errors, e.g.
NSData *myImageData = [NSData dataWithContentsOfURL:[[NSURL alloc] initWithString:myObject.thumbnailUrlString]]; // 1. Method returns an Objective-C object with a +0 retain count
myObject.myImageData = myImageData;
[myImageData release]; // 2. Incorrect decrement of the reference count of an object that is not owned at this point by the caller
You don't have ARC turned on. You almost certainly should turn on ARC so that the system will handle all of this for you.
That said, this is a basic manual memory management error, and the analyzer is telling you so.
myObject.myImageData = [NSData dataWithContentsOfURL:[[NSURL alloc] initWithString:myObject.thumbnailUrlString]];
This leaks the NSURL you created with +alloc. You need to call release on it at some point, but you no longer have a pointer to it. The usual way to fix this is with an autoreleased NSURL:
myObject.myImageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:myObject.thumbnailUrlString]];
But the much better way to fix it is to turn on ARC.
Your attempt at fixing it releases the wrong object. You don't own myImageData. You didn't create it with alloc, new, or copy, and you didn't call retain on it. The analyzer is warning you that you're incorrectly releasing it.
My CMPedometer is not running.
The code before it and after it gets run, but it itself does not work.
I get no warning or exception.
I'm testing it on a real 5s.
I've tried both querydata and startpedometerupdates.
I am importing core motion and the library is linked.
Any help?
if ([CMPedometer isStepCountingAvailable] == YES)
{
CMPedometer *cmped;
[cmped queryPedometerDataFromDate:start toDate:[NSDate date] withHandler:^(CMPedometerData *pedometerData, NSError *error){
stepslabel.text = [pedometerData.numberOfSteps stringValue];
}];
}
The problem with the original code above is the cmped variable gets deallocated at the end of the if statement, so the query is destroyed before it finishes.
By changing it to a strong property, it is retained in memory for the life of the class.
It seems really odd but I got it working by not declaring in the .h or before using it. What worked was declaring as #property CMPedometer *cmped; right after interface
I'm writing a Mac OSX application using Cocoa that is designed to stop working after a specified date, to avoid the user simply changing their system clock and then re-running the app I would like the program to close and delete itself if it is loaded after the expiry date. Is this possible?
I am distributing the application directly not through the app store. Also, checking the date using the internet isn't really an option because the app needs to be useable offline.
Thanks,
Matthew
It's possible, but not reliably so. To delete your app, just get your main bundle's URL and tell NSFileManager to delete it. But your app bundle may not be writable — and thus not deletable either — and the user may have any number of backups even if you do manage to delete it. I would not write anything that depends on this being possible unless I had tight control over the systems the program will run on. (I mean, I probably wouldn't write something that does this anyway, because it's a little crazy. But if I were going to write something like this, it would have to be something that only runs on my own systems.)
You could perform some sanity checks in the system to get an idea whether the user manually set the clock back to the past.
Note that I still don't think the plan of (maliciously) deleting user files is a great idea in general and the following approach in particular will certainly break under Sandboxing..
..but out of curiosity: Here's a snippet that will check all files in /var/log and return whether some of them have been modified in the future (= the system is quite likely running "in the past")
- (bool)isFakeSystemTime
{
int futureFileCount = 0;
// let's check against 1 day from now in the future to be safe
NSTimeInterval secondsPerDay = 24 * 60 * 60;
NSDate *tomorrow = [[[NSDate alloc] initWithTimeIntervalSinceNow:secondsPerDay] autorelease];
NSString *directoryPath = #"/var/log";
NSArray *filesInDirectory = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:directoryPath error:nil];
for (NSString* fileName in filesInDirectory)
{
NSDictionary *attributes = [[NSFileManager defaultManager] attributesOfItemAtPath:[directoryPath stringByAppendingPathComponent:fileName] error:nil];
NSDate *date = [attributes valueForKey:#"NSFileModificationDate"];
if (!date)
continue;
if ([date compare:tomorrow] == NSOrderedDescending)
{
NSLog(#"File '%#' modified >=1 day in the future", fileName);
futureFileCount++;
}
}
// again, some heuristic to be (more) on the safe side
return futureFileCount > 5;
}
My app currently have this sqlite file (lets name it v1)
What i want to do is that when i activate a IBAction , it will automatically delete the current file (v1) and retrieve values from webservice and store inside a new file (v2) and the application will then use the new sqlite file (v2)
any idea on how to implement?
my current code is here:
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (persistentStoreCoordinator != nil) {
return persistentStoreCoordinator;
}
NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: #"test.sqlite"]];
NSLog(#"%#",storeUrl);
NSError *error = nil;
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return persistentStoreCoordinator;
}
You can:
download the new database from the server
reset the whole Core Data context (store coordinator, managed object contexts, managed objects)
replace the old database with the new one
ask the UI to refresh to display the newest content: the Core Data context should reload lazily
But this approach is quite dangerous, as you'd have to make sure every Core Data object in your app can be reset. Also, replacing the database should happen just after resetting the context, to avoid a race condition. If you have threads / blocks accessing Core Data this is even more difficult.
A better approach may be to update the database records by downloading a JSON file that contains the new database's contents, delete the old records, and insert the new ones. This also makes sure that you can update your Core Data schema in a future version of the app without breaking your content updating process. And by using the NSFetchResultsController class, your table views or other UI elements may even update automatically with a nice animation as your database gets updated.
If you care about bandwidth, I use protocol buffers which are way more compact than any JSON or even sqlite file would be, and quite easy to use.
Background
I've already posted a question about the basics of sharing a Core Data store between processes.
I'm trying to implement the recommendations given and I'm running into problems.
My Goal
I have two processes - the Helper App and the UI. They both share a single data store. I want the UI to update it's NSManagedObjectContext when the Helper App has saved new data to the store.
Current Program Flow
The Helper App Process writes data to the Store.
In the Helper App, I listen for NSManagedObjectContextDidSaveNotification notifications.
When the context is saved, I encode the inserted, deleted and updated objects using their URI representations and NSArchiver.
I send an NSNotification to the NSDistributedNotificationCenter with this encoded dictionary as the userInfo.
The UI Process is listening for the save notification. When it receives the notification, it unarchives the userInfo using NSUnarchiver.
It looks up all the updated/inserted/deleted objects from the URIs given and replaces them with NSManagedObjects.
It constructs an NSNotification with the updated/inserted/deleted objects.
I call mergeChangesFromContextDidSaveNotification: on the Managed Object Context of the UI Process, passing in the NSNotification I constructed in the previous step.
The Problem
Inserted objects are faulted into the UI Managed Object Context fine and they appear in the UI. The problem comes with updated objects. They just don't update.
What I've tried
The most obvious thing to try would
be to pass the save Notification
from the Helper App process to the
UI process. Easy, right? Well, no.
Distributed Notifications won't
allow me to do that as the userInfo
dictionary is not in the right
format. That's why I'm doing all the
NSArchiving stuff.
I've tried calling
refreshObject:mergeChanges:YES on
the NSManagedObjects to be updated,
but this doesn't seem to have any
effect.
I've tried performing the
mergeChangesFromContextDidSaveNotification:
selector on the main thread and the
current thread. Neither seems to
affect the result.
I've tried using
mergeChangesFromContextDidSaveNotification:
before between threads, which of
course is much simpler and it worked
perfectly. But I need this same
functionality between processes.
Alternatives?
Am I missing something here? I'm consistently getting the feeling I'm making this much more complex than it needs to be, but after reading the documentation several times and spending a few solid days on this, I can't see any other way of refreshing the MOC of the UI.
Is there a more elegant way of doing this? Or am I just making a silly mistake somewhere in my code?
The Code
I've tried to make it as readable as possible, but it's still a mess. Sorry.
Helper App Code
-(void)workerThreadObjectContextDidSave:(NSNotification *)saveNotification {
NSMutableDictionary *savedObjectsEncodedURIs = [NSMutableDictionary dictionary];
NSArray *savedObjectKeys = [[saveNotification userInfo] allKeys];
for(NSString *thisSavedObjectKey in savedObjectKeys) {
// This is the set of updated/inserted/deleted NSManagedObjects.
NSSet *thisSavedObjectSet = [[saveNotification userInfo] objectForKey:thisSavedObjectKey];
NSMutableSet *thisSavedObjectSetEncoded = [NSMutableSet set];
for(id thisSavedObject in [thisSavedObjectSet allObjects]) {
// Construct a set of URIs that will be encoded as NSData
NSURL *thisSavedObjectURI = [[(NSManagedObject *)thisSavedObject objectID] URIRepresentation];
[thisSavedObjectSetEncoded addObject:thisSavedObjectURI];
}
// Archive the set of URIs.
[savedObjectsEncodedURIs setObject:[NSArchiver archivedDataWithRootObject:thisSavedObjectSetEncoded] forKey:thisSavedObjectKey];
}
if ([[savedObjectsEncodedURIs allValues] count] > 0) {
// Tell UI process there are new objects that need merging into it's MOC
[[NSDistributedNotificationCenter defaultCenter] postNotificationName:#"com.synapticmishap.lapsus.save" object:#"HelperApp" userInfo:(NSDictionary *)savedObjectsEncodedURIs];
}
}
UI Code
-(void)mergeSavesIntoMOC:(NSNotification *)notification {
NSDictionary *objectsToRefresh = [notification userInfo];
NSMutableDictionary *notificationUserInfo = [NSMutableDictionary dictionary];
NSArray *savedObjectKeys = [[notification userInfo] allKeys];
for(NSString *thisSavedObjectKey in savedObjectKeys) {
// Iterate through all the URIs in the decoded set. For each URI, get the NSManagedObject and add it to a set.
NSSet *thisSavedObjectSetDecoded = [NSUnarchiver unarchiveObjectWithData:[[notification userInfo] objectForKey:thisSavedObjectKey]];
NSMutableSet *savedManagedObjectSet = [NSMutableSet set];
for(NSURL *thisSavedObjectURI in thisSavedObjectSetDecoded) {
NSManagedObject *thisSavedManagedObject = [managedObjectContext objectWithID:[persistentStoreCoordinator managedObjectIDForURIRepresentation:thisSavedObjectURI]];
[savedManagedObjectSet addObject:thisSavedManagedObject];
// If the object is to be updated, refresh the object and merge in changes.
// This doesn't work!
if ([thisSavedObjectKey isEqualToString:NSUpdatedObjectsKey]) {
[managedObjectContext refreshObject:thisSavedManagedObject mergeChanges:YES];
[managedObjectContext save:nil];
}
}
[notificationUserInfo setObject:savedManagedObjectSet forKey:thisSavedObjectKey];
}
// Build a notification suitable for merging changes into MOC.
NSNotification *saveNotification = [NSNotification notificationWithName:#"" object:nil userInfo:(NSDictionary *)notificationUserInfo];
[managedObjectContext performSelectorOnMainThread:#selector(mergeChangesFromContextDidSaveNotification:)
withObject:saveNotification
waitUntilDone:YES];
}
I used the method in
http://www.mlsite.net/blog/?p=518
then every object is correctly faulted but the faults are fetch in cache so still no update
I had to do
[moc stalenessInterval = 0];
And it finally worked, with relationship.
You're looking for - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag I believe.
This will refresh the object with the info in the persistent store, merging changes if you want.
I'd go with Mike's suggestion and just watch the store file for changes.
Though it may not be the most efficient, I've had success using - [NSManagedObjectContext reset] from a second process when there's a change to a store. In my case case, the code is fairly linear — all I do is run a fetch request for some data after resetting. I don't know how this will work with bindings and a complicated UI, but you may be able to post a notification to manually update things if it's not handled automatically.
I had this exact same issue with an iPhone app that I've been working on. In my case, the solution involved setting the Context's stalenessInterval to something suitably infinitesimal (e.g., 0.5 seconds).
This works, except for sandboxes apps. You can't send a notification with a user info dict. Instead consider some other IPC like XPC or DO.
On a side note, using NSDustributedNotificationCenter is not always 100% if the system is busy.
Setting stalenessInterval of managed object context works. My case involves multiple threads instead of process though.
Starting with iOS 9, you should now use mergeChangesFromRemoteContextSave:intoContexts:. See this for an explanation: https://www.innoq.com/en/blog/ios-writing-core-data-in-today-extension/