05、线程同步

interface ViewController ()

//总票数

@property (nonatomic, assign) int ticketsCount;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.ticketsCount = 10;

}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {

//模拟买票窗口1

NSThread *thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(sellTickets) object:nil];

[thread1 start];

//模拟买票窗口2

NSThread *thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(sellTickets) object:nil];

[thread2 start];

}

//线程是不安全的

//模拟卖票的方法

- (void)sellTickets {

while (YES) {

//模拟耗时

[NSThread sleepForTimeInterval:1.0];

//任意一个对象内部都有一把锁

//加锁会影响程序的性能

//互斥锁

//线程同步

@synchronized(self) {

//判断还有没有票

if (self.ticketsCount > 0) {

self.ticketsCount = self.ticketsCount - 1;

NSLog(@"剩余%d张票",self.ticketsCount);

}else{

NSLog(@"来晚了，票没了");

break;

}

}

}

}

//输出两次9

//t1 t=10

//t2 t=10

//t1 t=9 log

//t2 t=9 log

//输出8，9

//t2 t=9

//t1 t=8 log

//t2 log

@end