dispatch_queue_t.m

#import "ViewController.h"
#import <AFNetworking/AFNetworking.h>

@interface ViewController ()

@end

static dispatch_queue_t _queue;

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    _queue = dispatch_get_global_queue(0, 0);
    dispatch_async(_queue, ^{
        NSLog(@"start-----");
        [self getNetwork];
        NSLog(@"end-----");
    });
}

- (void)getNetwork {
    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
    manager.responseSerializer = [AFHTTPResponseSerializer serializer];
    
    dispatch_semaphore_t semphore = dispatch_semaphore_create(0);
    
    NSString* urlStr = @"http://www.weather.com.cn/data/sk/101010100.html";
    
    [manager GET:urlStr parameters:nil progress:^(NSProgress * _Nonnull uploadProgress) {
        
    } success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
        
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:(NSData *)responseObject options:0 error:nil];
        NSLog(@"result: %@", json);
        dispatch_semaphore_signal(semphore);
        
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
    }];
    
    
    dispatch_semaphore_wait(semphore, DISPATCH_TIME_FOREVER);
}


@end