Download di un file di grandi dimensioni - iPhone SDK

Question

Sto utilizzando il metodo di download asincrono di Erica Sadun (link qui per il file di progetto: download), tuttavia il suo metodo non funziona con file di grandi dimensioni (50 MB o superiore). Se provo a scaricare un file sopra i 50 mb, di solito si blocca a causa di un crash di memoria. Posso comunque modificare questo codice in modo che funzioni anche con file di grandi dimensioni? Ecco il codice che ho nei Rami DownloadHelper (che è già nel link download):

.h

@protocol DownloadHelperDelegate <NSObject> 
@optional 
- (void) didReceiveData: (NSData *) theData; 
- (void) didReceiveFilename: (NSString *) aName; 
- (void) dataDownloadFailed: (NSString *) reason; 
- (void) dataDownloadAtPercent: (NSNumber *) aPercent; 
@end 

@interface DownloadHelper : NSObject 
{ 
    NSURLResponse *response; 
    NSMutableData *data; 
    NSString *urlString; 
    NSURLConnection *urlconnection; 
    id <DownloadHelperDelegate> delegate; 
    BOOL isDownloading; 
} 
@property (retain) NSURLResponse *response; 
@property (retain) NSURLConnection *urlconnection; 
@property (retain) NSMutableData *data; 
@property (retain) NSString *urlString; 
@property (retain) id delegate; 
@property (assign) BOOL isDownloading; 

+ (DownloadHelper *) sharedInstance; 
+ (void) download:(NSString *) aURLString; 
+ (void) cancel; 
@end 

.m

#define DELEGATE_CALLBACK(X, Y) if (sharedInstance.delegate && [sharedInstance.delegate respondsToSelector:@selector(X)]) [sharedInstance.delegate performSelector:@selector(X) withObject:Y]; 
#define NUMBER(X) [NSNumber numberWithFloat:X] 

static DownloadHelper *sharedInstance = nil; 

@implementation DownloadHelper 
@synthesize response; 
@synthesize data; 
@synthesize delegate; 
@synthesize urlString; 
@synthesize urlconnection; 
@synthesize isDownloading; 

- (void) start 
{ 
    self.isDownloading = NO; 

    NSURL *url = [NSURL URLWithString:self.urlString]; 
    if (!url) 
    { 
     NSString *reason = [NSString stringWithFormat:@"Could not create URL from string %@", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     return; 
    } 

    NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:url]; 
    if (!theRequest) 
    { 
     NSString *reason = [NSString stringWithFormat:@"Could not create URL request from string %@", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     return; 
    } 

    self.urlconnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; 
    if (!self.urlconnection) 
    { 
     NSString *reason = [NSString stringWithFormat:@"URL connection failed for string %@", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     return; 
    } 

    self.isDownloading = YES; 

    // Create the new data object 
    self.data = [NSMutableData data]; 
    self.response = nil; 

    [self.urlconnection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; 
} 

- (void) cleanup 
{ 
    self.data = nil; 
    self.response = nil; 
    self.urlconnection = nil; 
    self.urlString = nil; 
    self.isDownloading = NO; 
} 

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)aResponse 
{ 
    // store the response information 
    self.response = aResponse; 

    // Check for bad connection 
    if ([aResponse expectedContentLength] < 0) 
    { 
     NSString *reason = [NSString stringWithFormat:@"Invalid URL [%@]", self.urlString]; 
     DELEGATE_CALLBACK(dataDownloadFailed:, reason); 
     [connection cancel]; 
     [self cleanup]; 
     return; 
    } 

    if ([aResponse suggestedFilename]) 
     DELEGATE_CALLBACK(didReceiveFilename:, [aResponse suggestedFilename]); 
} 

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)theData 
{ 
    // append the new data and update the delegate 
    [self.data appendData:theData]; 
    if (self.response) 
    { 
     float expectedLength = [self.response expectedContentLength]; 
     float currentLength = self.data.length; 
     float percent = currentLength/expectedLength; 
     DELEGATE_CALLBACK(dataDownloadAtPercent:, NUMBER(percent)); 
    } 
} 

- (void)connectionDidFinishLoading:(NSURLConnection *)connection 
{ 
    // finished downloading the data, cleaning up 
    self.response = nil; 

    // Delegate is responsible for releasing data 
    if (self.delegate) 
    { 
     NSData *theData = [self.data retain]; 
     DELEGATE_CALLBACK(didReceiveData:, theData); 
    } 
    [self.urlconnection unscheduleFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; 
    [self cleanup]; 
} 

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
{ 
    self.isDownloading = NO; 
    NSLog(@"Error: Failed connection, %@", [error localizedDescription]); 
    DELEGATE_CALLBACK(dataDownloadFailed:, @"Failed Connection"); 
    [self cleanup]; 
} 

+ (DownloadHelper *) sharedInstance 
{ 
    if(!sharedInstance) sharedInstance = [[self alloc] init]; 
    return sharedInstance; 
} 

+ (void) download:(NSString *) aURLString 
{ 
    if (sharedInstance.isDownloading) 
    { 
     NSLog(@"Error: Cannot start new download until current download finishes"); 
     DELEGATE_CALLBACK(dataDownloadFailed:, @""); 
     return; 
    } 

    sharedInstance.urlString = aURLString; 
    [sharedInstance start]; 
} 

+ (void) cancel 
{ 
    if (sharedInstance.isDownloading) [sharedInstance.urlconnection cancel]; 
} 
@end 

E infine è così che scrivo la file con le due classi sopra:

- (void) didReceiveData: (NSData *) theData 
{ 
    if (![theData writeToFile:self.savePath atomically:YES]) 
     [self doLog:@"Error writing data to file"]; 

    [theData release]; 

} 

Se qualcuno potesse darmi una mano sarei così felice!

Grazie,

Kevin

Answer 1

Sostituire l'in-memory NSData *data con una NSOutputStream *stream. Nel -start creare il flusso di aggiungere e aprirlo:

stream = [[NSOutputStream alloc] initToFileAtPath:path append:YES]; 
[stream open]; 

Poiché i dati in arrivo, scriverlo al flusso:

NSUInteger left = [theData length]; 
NSUInteger nwr = 0; 
do { 
    nwr = [stream write:[theData bytes] maxLength:left]; 
    if (-1 == nwr) break; 
    left -= nwr; 
} while (left > 0); 
if (left) { 
    NSLog(@"stream error: %@", [stream streamError]); 
} 

Quando hai finito, chiudere il flusso:

[stream close]; 

Un approccio migliore sarebbe aggiungere il flusso oltre ai dati ivar, impostare l'helper come delegato del flusso, bufferizzare i dati in entrata nel data ivar, quindi scaricare i contenuti di ivar dei dati nell'helper wh sempre il flusso invia l'aiuto al suo evento disponibile nello spazio e lo cancella dai dati ivar.

Answer 2

Ho una leggera modifica al codice precedente.

Utilizzare questa funzione, funziona correttamente per me.

Answer 3

Prova AFNetworking. E:

NSString *yourFileURL=@"http://yourFileURL.zip"; 
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:yourFileURL]]; 
AFURLConnectionOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request]; 

NSString *cacheDir = [NSSearchPathForDirectoriesInDomains 
          (NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0]; 
NSString *filePath = [cacheDir stringByAppendingPathComponent: 
         @"youFile.zip"]; 

operation.outputStream = [NSOutputStream outputStreamToFileAtPath:filePath append:NO]; 

[operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) { 
    //show here your downloading progress if needed 
}]; 

[operation setCompletionBlock:^{ 
    NSLog(@"File successfully downloaded"); 
}]; 

[operation start];