NSURLSession官方编程指南学习

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Listing 1-1  Sample delegate class interface

#import <Foundation/Foundation.h>

typedef void (^CompletionHandlerType)();

@interface MySessionDelegate : NSObject <NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>

@property NSURLSession *backgroundSession;
@property NSURLSession *defaultSession;
@property NSURLSession *ephemeralSession;

#if TARGET_OS_IPHONE
@property NSMutableDictionary *completionHandlerDictionary;
#endif

- (void) addCompletionHandler: (CompletionHandlerType) handler forSession: (NSString *)identifier;
- (void) callCompletionHandlerForSession: (NSString *)identifier;

@end

#if TARGET_OS_IPHONE
self.completionHandlerDictionary = [NSMutableDictionary dictionaryWithCapacity:0];
#endif

/* Create some configuration objects. */

NSURLSessionConfiguration *backgroundConfigObject = [NSURLSessionConfiguration backgroundSessionConfiguration: @"myBackgroundSessionIdentifier"];
NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSessionConfiguration *ephemeralConfigObject = [NSURLSessionConfiguration ephemeralSessionConfiguration];


/* Configure caching behavior for the default session.Note that iOS requires the cache path to be a path relative to the ~/Library/Caches directory, but OS X expects an absolute path.*/

#if TARGET_OS_IPHONE
NSString *cachePath = @"/MyCacheDirectory";

NSArray *myPathList = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *myPath    = [myPathList  objectAtIndex:0];

NSString *bundleIdentifier = [[NSBundle mainBundle] bundleIdentifier];

NSString *fullCachePath = [[myPath stringByAppendingPathComponent:bundleIdentifier] stringByAppendingPathComponent:cachePath];
NSLog(@"Cache path: %@\n", fullCachePath);
#else
NSString *cachePath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"/nsurlsessiondemo.cache"];

NSLog(@"Cache path: %@\n", cachePath);
#endif


NSURLCache *myCache = [[NSURLCache alloc] initWithMemoryCapacity: 16384 diskCapacity: 268435456 diskPath: cachePath];
defaultConfigObject.URLCache = myCache;
defaultConfigObject.requestCachePolicy = NSURLRequestUseProtocolCachePolicy;

/* Create a session for each configurations. */

self.defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]];
self.backgroundSession = [NSURLSession sessionWithConfiguration: backgroundConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]];
self.ephemeralSession = [NSURLSession sessionWithConfiguration: ephemeralConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]];

Listing 1-3  Creating a second session with the same configuration object

ephemeralConfigObject.allowsCellularAccess = NO;
// ...

NSURLSession *ephemeralSessionWiFiOnly = [NSURLSession sessionWithConfiguration: ephemeralConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]];

Listing 1-4  Requesting a resource using system-provided delegates
NSURLSession *delegateFreeSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate: nil delegateQueue: [NSOperationQueue mainQueue]];

[[delegateFreeSession dataTaskWithURL: [NSURL URLWithString: @"http://www.example.com/"]
                    completionHandler:^(NSData *data, NSURLResponse *response,
                                        NSError *error) {
                        NSLog(@"Got response %@ with error %@.\n", response, error);
                        NSLog(@"DATA:\n%@\nEND DATA\n",
                              [[NSString alloc] initWithData: data
                                                    encoding: NSUTF8StringEncoding]);
                    }] resume];

Listing 1-5 shows how you create and start a data task. Data task example

NSURL *url = [NSURL URLWithString: @"http://www.example.com/"];

NSURLSessionDataTask *dataTask = [self.defaultSession dataTaskWithURL: url];

[dataTask resume];

Listing 1-6  Download task example

NSURL *url = [NSURL URLWithString: @"https://developer.apple.com/library/ios/documentation/Cocoa/Reference/"
              "Foundation/ObjC_classic/FoundationObjC.pdf"];

NSURLSessionDownloadTask *downloadTask = [self.backgroundSession downloadTaskWithURL: url];
[downloadTask resume];

Listing 1-7  Delegate methods for download tasks
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
    NSLog(@"Session %@ download task %@ finished downloading to URL %@\n",
          session, downloadTask, location);
   
#if 0
    /* Workaround */
    [self callCompletionHandlerForSession:session.configuration.identifier];
#endif
   
#define READ_THE_FILE 0
#if READ_THE_FILE
    /* Open the newly downloaded file for reading. */
    NSError *err = nil;
    NSFileHandle *fh = [NSFileHandle fileHandleForReadingFromURL:location
                                                           error: &err];
   
    /* Store this file handle somewhere, and read data from it. */
   
#else
    NSError *err = nil;
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSString *cacheDir = [[NSHomeDirectory()
                           stringByAppendingPathComponent:@"Library"]
                          stringByAppendingPathComponent:@"Caches"];
    NSURL *cacheDirURL = [NSURL fileURLWithPath:cacheDir];
    if ([fileManager moveItemAtURL:location
                             toURL:cacheDirURL
                             error: &err]) {
       
        /* Store some reference to the new URL */
    } else {
        /* Handle the error. */
    }
#endif
   
}

-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
    NSLog(@"Session %@ download task %@ wrote an additional %lld bytes (total %lld bytes) out of an expected %lld bytes.\n",
          session, downloadTask, bytesWritten, totalBytesWritten, totalBytesExpectedToWrite);
}

-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes
{
    NSLog(@"Session %@ download task %@ resumed at offset %lld bytes out of an expected %lld bytes.\n",
          session, downloadTask, fileOffset, expectedTotalBytes);
}

Listing 1-8  Session delegate methods for iOS background downloads

#if TARGET_OS_IPHONE
-(void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session
{
    NSLog(@"Background URL session %@ finished events.\n", session);
   
    if (session.configuration.identifier)
        [self callCompletionHandlerForSession: session.configuration.identifier];
}

- (void) addCompletionHandler: (CompletionHandlerType) handler forSession: (NSString *)identifier
{
    if ([ self.completionHandlerDictionary objectForKey: identifier]) {
        NSLog(@"Error: Got multiple handlers for a single session identifier.  This should not happen.\n");
    }
   
    [ self.completionHandlerDictionary setObject:handler forKey: identifier];
}

- (void) callCompletionHandlerForSession: (NSString *)identifier
{
    CompletionHandlerType handler = [self.completionHandlerDictionary objectForKey: identifier];
   
    if (handler) {
        [self.completionHandlerDictionary removeObjectForKey: identifier];
        NSLog(@"Calling completion handler.\n");
       
        handler();
    }
}
#endif

Listing 1-9  App delegate methods for iOS background downloads

- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler
{
    NSURLSessionConfiguration *backgroundConfigObject = [NSURLSessionConfiguration backgroundSessionConfiguration: identifier];
   
    NSURLSession *backgroundSession = [NSURLSession sessionWithConfiguration: backgroundConfigObject delegate: self.mySessionDelegate delegateQueue: [NSOperationQueue mainQueue]];
   
    NSLog(@"Rejoining session %@\n", identifier);
   
    [ self.mySessionDelegate addCompletionHandler: completionHandler forSession: identifier];
}

NSURLSession官方编程指南学习

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原文地址：http://blog.csdn.net/longshihua/article/details/51272024