IOS多线程加锁

注意：加锁位置不同产生结果不同

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
 
    //设置中票数
    self.totalCount = ;
 
     self.threadA = [[NSThread alloc]initWithTarget:self selector:@selector(saleTicket) object:nil];
     self.threadB = [[NSThread alloc]initWithTarget:self selector:@selector(saleTicket) object:nil];
     self.threadC = [[NSThread alloc]initWithTarget:self selector:@selector(saleTicket) object:nil];
 
    self.threadA.name = @"售票员A";
    self.threadB.name = @"售票员B";
    self.threadC.name = @"售票员C";
 
    //启动线程
        [self.threadA start];
        [self.threadB start];
        [self.threadC start];
}
 
-(void)saleTicket
{
    while () {
 
    //锁:必须是全局唯一的
    //1.注意枷锁的位置
    //2.注意枷锁的前提条件,多线程共享同一块资源
    //3.注意加锁是需要代价的,需要耗费性能的
    //4.加锁的结果:线程同步
 
    @synchronized(self) {
        //线程1
        //线程2
        //线程3
        NSInteger count = self.totalCount;
        if (count >) {
 
            for (NSInteger i = ; i<; i++) {
            }
 
            self.totalCount = count - ;
            //卖出去一张票
            NSLog(@"%@卖出去了一张票,还剩下%zd张票", [NSThread currentThread].name,self.totalCount);
        }else
        {
            NSLog(@"不要回公司上班了");
            break;
        }
        }
    }
 
}