I got a problem , How to know the file is accessible ???
For example , the file is writing , but not finish yet.
And I check the file again ,
I use
[[NSFileManager defaultManager] fileExistsAtPath:filePath];
It return true ... but the file is not accessible .
How to determine the file is ready ?
Thanks
Webber
EDIT
Maybe I'm not telling my problem clearly . I mean if you start transport a video file . before transport finish . the video file is not accessible , but you still can get a part of transporting file.
Write Data in async way using GCD concept and once it is completed, the completion handler will be executed.(Where completion of a writing process shall be detected)
The dispatch I/O convenience API lets you perform asynchronous read and write operations on file descriptors. This API supports stream-based semantics for accessing the contents of the file-descriptor.
Method:
void dispatch_write ( dispatch_fd_t fd, dispatch_data_t data, dispatch_queue_t queue, void (^handler)(dispatch_data_t data, int error) );
Ref: https://developer.apple.com/library/ios/documentation/Performance/Reference/GCD_libdispatch_Ref/index.html#//apple_ref/c/func/dispatch_write
Basically you need to check the attributes of the file and particullary the NSFileBusy attribute:
if ([fileManager fileExistsAtPath:filePath]) {
NSDictionary *attributes = [fileManager attributesOfItemAtPath:filePath error:nil];
NSLog(#"File Busy %#", [attributes objectForKey:NSFileBusy]);
}
NSFileCoordinator and NSFilePresenter are created just for that. You may find interesting Advanced iCloud Document Storage video from wwdc that covers the usage of this classes. Building a Document-based App will be great to watch too.
Try to fetch data of file by using following code :
NSURL *url = [NSURL fileURLWithPath:filePath];
NSData *readData = [NSData dataWithContentsOfURL:url];
Related
I'm creating an app that plays back multiple videos and photos in a snapchat story fashion. I fetch each of these videos data and write it to a temp file in order to play with AVPlayer.
NSString *outputPath = [[NSString alloc] initWithFormat:#"%#%#", NSTemporaryDirectory(), [NSString stringWithFormat:#"output%i.mov", i]];
[data writeToFile:outputPath atomically:YES];
In viewWillDissapear I delete all of these files with:
NSArray* tmpDirectory = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:NSTemporaryDirectory() error:NULL];
for (NSString *file in tmpDirectory) {
[[NSFileManager defaultManager] removeItemAtPath:[NSString stringWithFormat:#"%#%#", NSTemporaryDirectory(), file] error:NULL];
}
But when I look at how much memory my app is using, in settings, its around 300 mb. Is there a way to see what is actually taking up all this memory? I would think this is high since I'm not caching anything besides the currentUser data (name, profileImage).
Should I be doing something else to clean the temp files?
But this line is absolutely wrong:
[data writeToFile:outputPath atomically:YES];
The implication is that at some moment — this moment — you are holding an entire video in memory (as data). That is completely incorrect; it should never happen. You should download to a file on disk, and if necessary, write that file to another file; you should never attempt to load the entire video into memory at once.
As #peter mentioned, you can use streaming Video streaming.
Or else If you really want to download video file and store it into the disk space and want to utilize it later part then you should follow apple recommended way i.e NSFileHandle class to optimize your application heap memory while downloading larger files.
NSFileHandle
I stored an audio file of format .aiff in two different folders. The NSData is returning nil for one file path even though both file paths have the audio file. I double checked the file paths.
The path is like this:
//url1 file:///Users/VenkataManiteja/Library/Developer/CoreSimulator/Devices/80B8117E-D2C9-4B42-8A76-9A89A10FB1C1/data/Containers/Data/Application/FD17AD64-EAF9-4578-B50D-0B5BF6F2DEFF/Documents/28Apr15_090827AM.aif
//url2 file:///Users/VenkataManiteja/Library/Developer/CoreSimulator/Devices/80B8117E-D2C9-4B42-8A76-9A89A10FB1C1/data/Containers/Data/Application/B60CF270-73CA-4BE4-BA75-B2AC3642360D/Documents/28Apr15_090827AM.aif
NSError *err;
data = [NSData dataWithContentsOfURL:url1]; //this is working fine
audioPlayer = [[AVAudioPlayer alloc] initWithData:data error:&err];
data = [NSData dataWithContentsOfURL:url2]; //nsdata is returning nil
Can anyone tell me why the url2 is getting the nil NSData?
You are trying to read a file outside of the running app's sandbox. While both may exist, presumably you are running the application with ID "FD17AD64-EAF9-4578-B50D-0B5BF6F2DEFF", which is why that URL is working while the other one isn't.
I would recommend watching the WWDC video A Practical Guide to the App Sandbox for more on how the security model works.
I want to read a list (in plain text) from a remote file line by line.
I have found some answers but they're not the ones I'm looking for.
p.s. I've been programing in objective-c and developing in iOS for about 2 months, I'm a rookie i might not understand or recognize some terms. Please answer like you are talking to a beginner.
If i am not wrong you just want to read a text from remote file, so here it is.
NSString * result = NULL;
NSError *err = nil;
NSURL * urlToRequest = [NSURL URLWithString:#"YOUR_REMOTE_FILE_URL"];//like "http://www.example.org/abc.txt"
if(urlToRequest)
{
result = [NSString stringWithContentsOfURL: urlToRequest
encoding:NSUTF8StringEncoding error:&err];
}
if(!err){
NSLog(#"Result::%#",result);
}
To load the remote txt file, you should take a look at NSURLConnection or AFNetworking (there are other possibilities, these two are probably the most common).
You will then get the content of the file. Depending on what you intend to do with it, you may have to parse it, either with something as simple as -[NSString componentsSeparatedByString:] or with something a bit more powerful like NSScanner.
There are three steps involved in loading a file
create the object that specifies the location of the file
call the appropriate NSString class method to load the file into a
string
handle the error if the file is not found
In step 1, you need to either create an NSString with the full path to the file in the file system, or you need to create an NSURL with the network location of the file. In the example below, the code creates an NSURL since your file is on the network.
In step 2, use the stringWithContentsOfFile method to load a file from the file system, or the stringWithContentsOfURL method to load a file from the network. In either case, you can specify the file encoding, or ask iOS to auto-detect the file encoding. The code below auto detects while loading from the network.
In step 3, the code below dumps the file to the debug console if successful or dumps the error object to the console on failure.
Missing from this code is multithreading. The code will block until the file is loaded. Running the code on a background thread, and properly notifying the main thread when the download is complete, is left as an exercise for the reader.
NSURL *url = [NSURL URLWithString:#"www.example.com/somefile.txt"];
NSStringEncoding encoding;
NSError *error;
NSString *str = [NSString stringWithContentsOfURL:url usedEncoding:&encoding error:&error];
if ( str )
NSLog( #"%#", str );
else
NSLog( #"%#", error );
I am working on a project where I need to manage videos. I need to rename or delete video. For that we need to hold the video in NSDATA and then manage it.
But I am getting an error message as Terminated due to memory error on below statement.
Edited
NSData *data=[NSData dataWithContentsOfFile:self.path];
if (data){
BOOL success = [data writeToFile:videopath atomically:NO];
}
self.path contains the path of video file. It works in small size video (of 4-10 mins) But it crashes in large size video (bigger than 20-30 mins).
Please advice.
Use this code instead loading the video file to memory, Your code will work with small files but u gonna fail with big files.
if ( [[NSFileManager defaultManager] isReadableFileAtPath:source] ){
[[NSFileManager defaultManager] copyItemAtURL:source toURL:destination error:nil];}
You are maintaing the full video as NSData inside the application. Instead of using a Video file as NSData, copy the video to some where (e.g NSTempoaryDirectoy). You can delete or rename the Old video.
I am not sure what the requirement for you. from your question I understood that you need to rename your video file. for renaming, why we need to go for reading it as NSdata and again writing the same. for Renaming try the below code.
NSFileManager *filemanager = [NSFileManager defaultManager];
if ([filemanager fileExistsAtPath:filePath])
{
NSString *target = [[filePath stringByDeletingLastPathComponent] stringByAppendingPathComponent:newnameofthefile];
[filemanager moveItemAtPath:filePath toPath:target error:nil];
}
I hope this may help you..
My app is using a core data SQLite database. I would like to enable my users to use iCloud to sync it between devices - and I was thinking I could use UIManagedDocument.
I subclassed it, following Apple's documentation, and it is works when a new persistent store file needs to be created. However, when I try to use it to open my old persistent store file, I get the following exception thrown error:
"UIManagedDocument can only read documents that are file packages"
Does this mean that I need to migrate the old persistent store to a new store managed by UIManagedDocument? If so, do I need to do this manually (i.e. read each record one-at-a-time from the old store and write it into the new one)?
Thanks in advance!
UIManagedDocument creates packages(folders) rather than atomic stores. The store is still there but its buried in the package. If you right click on the file that is created in your Documents folder in the simulator you'll be able to see the structure. The default is
mydocument.foo
-> StoreContent
-> persistentStore
What you need to do is create a new extension for your app file type so for example if your database extension is .myappdb you need to create a new document type in your project settings which might be .myappdbw. You can copy all settings from the entry for .myappdb
Next at the point where you handle opening your legacy document at mydocumenturl instead of passing that to your persistent store co-ordinator you create the directory structure above.
NSURL *newurl = [[mydocumenturl URLByDeletingPathExtension] URLByAppendingPathExtension:#"myappdbw"];
NSURL *desturl = [newurl URLByAppendingPathComponent:#"StoreContent"];
[[NSFileManager defaultManager] createDirectoryAtURL:desturl withIntermediateDirectories:YES attributes:nil error:NULL];
NSURL *finalurl = [desturl URLByAppendingPathComponent:#"persistentStore"];
and then move the legacy database into the folder system you have created
[[NSFileManager defaultManager] moveItemAtURL:mydocumenturl toURL:finalurl error:NULL];
and then you can pass the bundle url to UIManagedDocument
UIManagedDocument *doc = [[UIManagedDocument alloc] initWithFileURL:newurl];
A link which will be useful for the iCloud integration is
http://developer.apple.com/library/ios/#releasenotes/DataManagement/RN-iCloudCoreData/_index.html
Its all a bit mysterious as the most of the promised sample code has failed to appear so far but on the other hand its mostly fairly simple to deduce. Have a look at WWDC2011 sessions 107,116 and 315 for more hints.
But note that if you are going to use this method for migrating your legacy docs DONT set the NSPersistentStoreUbiquitousContentNameKey at point you migrate because the package changes when you do. The doc above describes it quite well.
Thanks for this tip. I think I found an even simpler solution.
I just create a new UIManagedDocument with a different filename than my old persistent store location.
In my subclassed UIManagedDocument, I override the configurePersistentStoreCoordinatorForURL method and do the migration once there:
- (BOOL)configurePersistentStoreCoordinatorForURL:(NSURL *)storeURL ofType:(NSString *)fileType modelConfiguration:(NSString *)configuration storeOptions:(NSDictionary *)storeOptions error:(NSError **)error
{
// If legacy store exists, copy it to the new location
NSFileManager* fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:legacyPersistentStoreURL.path])
{
NSError* thisError = nil;
[fileManager copyItemAtURL:legacyPersistentStoreURL toURL:storeURL error:&thisError];
[fileManager removeItemAtURL:legacyPersistentStoreURL error:&thisError];
}
return [super configurePersistentStoreCoordinatorForURL:storeURL ofType:fileType modelConfiguration:configuration storeOptions:storeOptions error:error];
}