////  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
      
        *)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