IOS NSThread（线程同步）

@interface HMViewController ()
/** 剩余票数 */
@property (nonatomic, assign) int leftTicketsCount;
@property (nonatomic, strong) NSThread *thread0;
@property (nonatomic, strong) NSThread *thread1;
@property (nonatomic, strong) NSThread *thread2;
@end

@implementation HMViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    // 默认有100张
    self.leftTicketsCount = 100;
    
    // 开启多条线程同时卖票
    self.thread0 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
    self.thread0.name = @"售票员 A";
//    self.thread0.threadPriority = 0.0;
    
    self.thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
    self.thread1.name = @"售票员 B";
//    self.thread1.threadPriority = 1.0;
    
    self.thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
    self.thread2.name = @"售票员 C";
//    self.thread2.threadPriority = 0.0;
}

/**
 * 卖票
 */
- (void)saleTicket
{
    while (1) {
        @synchronized(self) { // 加锁(只能用一把锁)
            // 1.先检查票数
            int count = self.leftTicketsCount;
            if (count > 0) {
                // 暂停
//                [NSThread sleepForTimeInterval:0.0002];
                
                // 2.票数 - 1
                self.leftTicketsCount = count - 1;
                
                NSThread *current = [NSThread currentThread];
                NSLog(@"%@ 卖了一张票, 剩余%d张票", current.name, self.leftTicketsCount);
            } else {
                // 退出线程
                [NSThread exit];
            }
        } // 解锁
    }
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self.thread0 start];
    [self.thread1 start];
    [self.thread2 start];
}