ios33--线程安全

//
//  ViewController.m
//  05-掌握-线程安全
//
//  多线程下载文件：每个线程下的部分可能是交错的，到时候就拼接不了。除非每个线程下载的不是交错的，而是从头到尾依次分开的，到时候就可以拼接了。

#import "ViewController.h"

@interface ViewController ()
/** 售票员A */
@property (nonatomic, strong) NSThread *threadA;
/** 售票员B */
@property (nonatomic, strong) NSThread *threadB;
/** 售票员C */
@property (nonatomic, strong) NSThread *threadC;

@property (nonatomic, assign) NSInteger totalCount;
@end

@implementation ViewController

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    
    //设置中票数
    self.totalCount = 100;
    
     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
    //@synchronized(self) {
        [self.threadA start];
        [self.threadB start];
        [self.threadC start];
    //}
    
}

-(void)saleTicket
{
    while (1) {
        
    //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
    //5.锁定1份代码只用1把锁，用多把锁是无效的

    @synchronized(self) {
        //线程1
        //线程2
        //线程3
        NSInteger count = self.totalCount;
        if (count >0) {
            
            for (NSInteger i = 0; i<1000000; i++) {
            }
            
            self.totalCount = count - 1;
            //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;
        }
        }
    }
    
}

@end