线程锁-生产者与消费者

#import "ViewController.h"

@interface ViewController ()


@property (nonatomic,strong) NSLock *lock;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //创建了一个线程锁
    self.lock = [[NSLock alloc]init];
    
    NSThread *thread1 = [[NSThread alloc]initWithTarget:self selector:@selector(eat) object:nil];
    thread1.name = @"夏洛";
    [thread1 start];
    
    NSThread *thread2 = [[NSThread alloc]initWithTarget:self selector:@selector(eat) object:nil];
    thread2.name = @"马冬梅";
    [thread2 start];
    
    NSThread *thread3 = [[NSThread alloc]initWithTarget:self selector:@selector(eat) object:nil];
    thread3.name = @"秋雅";
    [thread3 start];
}

- (void)eat{
    static int num = 5;
    while (1) {
        //加锁之后 同一时刻只允许一个线程访问
        //加锁  数据修改之前
        [self.lock lock];
        num --;
        NSLog(@"%@吃了一碗茴香打卤面 还剩……%d碗",[NSThread currentThread].name,num);
        [NSThread sleepForTimeInterval:2.f];
        if (num == 0) {
            break;
        }
        
        //解锁 数据修改完成
        [self.lock unlock];
    }
}

@end

屏幕快照 2019-04-25 下午3.34.05.png