Unzipping file on the device crashes due to timeout

Question

I am trying to unzip a file which is being downloaded through URL. The file downloaded is in zip format. I have used library : iPhone Unzip code which has SSZipArchive Library. It is used in current code to unzip the file once downloaded. But when I run the app as a stand alone application crashes by giving the log errors : example.app failed to launch in time. I am not sure if I can use this library or is there any other library which has been tried, tested and have it running on the device.

- (void)viewDidLoad {
   [super viewDidLoad];

    NSFileManager *fileManager = [NSFileManager defaultManager];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *directoryPath = [paths objectAtIndex:0];
    NSString *filePath = [NSString stringWithFormat:@"%@/ZipFiles.zip", directoryPath];

    NSString* updateURL = @"http://www.example.com/test.php?id=11";
    NSData* updateData = [NSData dataWithContentsOfURL: [NSURL URLWithString: updateURL] ];

    [fileManager createFileAtPath:filePath contents:updateData attributes:nil];
    /* SSZipArchive is a free API built on ZipArchive to unzip the files. Header file is passed in this class.*/

    [SSZipArchive unzipFileAtPath:filePath toDestination:directoryPath];
    NSLog(@"Finished unzipping database");
 }

Answer 1

The viewDidLoad method is being called from the main thread of the application and since the download and unzip operations are taking a significant amount of time, it is freezing the main thread. This is why you are seeing that error.

You need to move long running operations to a background thread so that the main thread is free to finish loading the application. There are many ways to do this and I prefer using blocks.

I suggest you read the Concurrency Programming Guide in the docs:

http://developer.apple.com/library/ios/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40008091