通过GCD、NSOperationQueue队列、NSThread三种方法来创建多线程

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *remindLabel;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
- (IBAction)sendBtnClick:(UIButton *)sender {

    /*--第一种采用GCD发送请求并刷新UI--*/
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        sleep(2);

        dispatch_async(dispatch_get_main_queue(), ^{

            _remindLabel.text=@"发送成功";
        });

    });
     /*--第二种采用NSBlockOperation、NSOperationQueue队列发送请求并刷新UI--*/
     NSOperationQueue *myQueue=[[NSOperationQueue alloc]init];
     NSBlockOperation *operation=[NSBlockOperation blockOperationWithBlock:^{
       //延时2秒
        sleep(2);
        //主线程刷新UI
        dispatch_async(dispatch_get_main_queue(), ^{

             _remindLabel.text=@"发送成功";
        });
    }];
    [myQueue addOperation:operation];

    /*--第三种采用NSThread发送请求并刷新UI--*/
    [NSThread detachNewThreadSelector:@selector(sendState) toTarget:self withObject:nil];

}
-(void)sendState
{
    sleep(2);
    dispatch_async(dispatch_get_main_queue(), ^{

        [self updateLabel];
    });
}
-(void)updateLabel
{
   _remindLabel.text=@"发送成功";
}
@end