线程锁

#import "ViewController.h"

@interface ViewController ()
//总票数
@property (nonatomic,assign) NSInteger count;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.count = 100;
    
}
- (IBAction)didClickSell:(id)sender {
    
    //线程锁
    NSLock *lockObject = [[NSLock alloc] init];
    for (int i = 0; i < 100;i++) {
       //并行队列
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            [lockObject lock];
            NSLog(@"我买到了第%ld张票",(long)self.count);
            self.count--;
            [lockObject unlock];
        });
    }
    
}