系统的代理方法
@interface AFURLSessionManagerTaskDelegate : NSObject <NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>
KVO
- (instancetype)initWithTask:(NSURLSessionTask *)task {
self = [super init];
if (!self) {
return nil;
}
_mutableData = [NSMutableData data];
_uploadProgress = [[NSProgress alloc] initWithParent:nil userInfo:nil];
_downloadProgress = [[NSProgress alloc] initWithParent:nil userInfo:nil];
__weak __typeof__(task) weakTask = task;
for (NSProgress *progress in @[ _uploadProgress, _downloadProgress ])
{
progress.totalUnitCount = NSURLSessionTransferSizeUnknown;
progress.cancellable = YES;
progress.cancellationHandler = ^{
[weakTask cancel];
};
progress.pausable = YES;
progress.pausingHandler = ^{
[weakTask suspend];
};
if ([progress respondsToSelector:@selector(setResumingHandler:)]) {
progress.resumingHandler = ^{
[weakTask resume];
};
}
[progress addObserver:self
forKeyPath:NSStringFromSelector(@selector(fractionCompleted))
options:NSKeyValueObservingOptionNew
context:NULL];
...
