iOS开发多线程篇---线程锁(线程安全)

   

@interface BTThreadViewController ()
{
    NSThread *OneThread;//师傅一
    NSThread *TwoThread;//师傅二
    NSThread *ThreeThread;//师傅三
    int allCake;//蛋糕总数
}
@end
@implementation BTThreadViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    
    [self myThread];
}
-(void)myThread
{
    allCake = 10;
    
    //给每个线程起一个名字,方便下面区分
    OneThread = [[NSThread alloc] initWithTarget:self selector:@selector(SendTheCake) object:nil];
    OneThread.name = @"师傅一";
    [OneThread start];
    
    TwoThread = [[NSThread alloc] initWithTarget:self selector:@selector(SendTheCake) object:nil];
    TwoThread.name = @"师傅二";
    [TwoThread start];
    
    ThreeThread = [[NSThread alloc] initWithTarget:self selector:@selector(SendTheCake) object:nil];
    ThreeThread.name = @"师傅三";
    [ThreeThread start];
}
-(void)SendTheCake
{
    while (1) {
        //线程锁的优点:能有效防止因多线程抢夺资源造成的数据安全问题
        //缺点:需要消耗大量的CPU资源,线程锁的使用前提:多条线程抢夺同一块资源
        //相关专业术语:线程同步,多条线程按顺序地执行任务。线程锁,就是使用了线程同步技术
        @synchronized(self){
            if (allCake > 0) {
                
                //线程休眠时间
                [NSThread sleepForTimeInterval:0.002];
                
                //蛋糕个数-1
                allCake -= 1;
                //打印当前的线程和剩余蛋糕数量
                NSThread *senderThread = [NSThread currentThread];
                NSLog(@"--%@发了1个蛋糕,还剩下%d个蛋糕",senderThread,allCake);
            }
            else
            {
                //退出线程
                [NSThread exit];
            }
        }
    }
}

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