网络请求

#import "ViewController.h"

@interface ViewController () <NSURLConnectionDataDelegate>
/** runLoop */
@property (nonatomic, assign) CFRunLoopRef runLoop;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 如果在子线程中使用NSURLConnection发送请求是不会有效果,因为子线程的runloop没有启动
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        NSURLConnection *conn = [NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com/images/234234324limgAB/2342lkjasdf3kkkkk.jpg"]] delegate:self];
        // 决定代理方法在哪个队列中执行
        [conn setDelegateQueue:[[NSOperationQueue alloc] init]];
        
        // 启动子线程的runLoop
//        [[NSRunLoop currentRunLoop] run];
        
        // 保存当前runloop
        self.runLoop = CFRunLoopGetCurrent();
        
        // 启动runLoop
        CFRunLoopRun();
    });
}

#pragma mark - <NSURLConnectionDataDelegate>
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"didReceiveResponse******%@", [NSThread currentThread]);
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    
    NSLog(@"didReceiveData******%@", [NSThread currentThread]);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"connectionDidFinishLoading******%@", [NSThread currentThread]);
    
    // 停止RunLoop
    CFRunLoopStop(self.runLoop);
}

@end