多线程的使用实列-卖票系统

标签：

#import "ViewController.h"

@interface ViewController ()

{

    UILabel *showLable;

    int curTicketNum;

    int saleTicketNum;

    NSString *saleWindowName;

    NSCondition *conditionClock;

}

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    //卖票系统 分3个窗口同时销售

    //默认100张票

    curTicketNum = 100;

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];

    button.frame = CGRectMake(100, 20, 150, 50);

    [self.view addSubview:button];

    [button setTitle:@"卖票了" forState:UIControlStateNormal];

    button.backgroundColor = [UIColor redColor];

    [button addTarget:self action:@selector(startSale) forControlEvents:UIControlEventTouchUpInside];

    showLable = [[UILabel alloc]initWithFrame:CGRectMake(0, 200, 375, 200)];

    [self.view addSubview:showLable];

    showLable.numberOfLines =3;

    showLable.textAlignment = NSTextAlignmentCenter;

    showLable.text = @"剩余票数：100张";

    showLable.font = [UIFont boldSystemFontOfSize:20];

    showLable.backgroundColor = [UIColor orangeColor];

}

//三个窗口同时卖票

- (void)startSale

{

    //初始化3个线程 每一个线程都是一个窗口

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

    firstWindow.name = @"售票<窗口1>";

    [firstWindow start];

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

    secondtWindow.name = @"售票<窗口2>";

    [secondtWindow start];

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

    thirdWindow.name = @"售票<窗口3>";

    [thirdWindow start];

//    NSCondition 是一个线程锁（条件锁）

    conditionClock = [[NSCondition alloc]init];

}

- (void)saleTicket

{

    //没有使用线程锁 3个线程（窗口）会同时访问卖票的方法 当剩余的票数是0 的时候其他线程还会继续访问，不知道剩余票数为0 ，继续访问剩余票数就有负数的情况

    //解决这个问题可以使用线程锁；只允许一个线程访问完毕之后另外一个线程再去访问

    while (curTicketNum > 0) {

        //使用线程锁只允许一个线程取访问

        [conditionClock lock];

        saleWindowName = [NSThread currentThread].name;

        [NSThread sleepForTimeInterval:0.1];

        //当前票数(剩余)

        curTicketNum -= 1;

        //卖的票数

        saleTicketNum = 100-curTicketNum;

        [self performSelectorOnMainThread:@selector(updateUI) withObject:nil waitUntilDone:YES];

        if (curTicketNum > 0) {

            [conditionClock unlock];

        }

    }

}

//更新界面

- (void)updateUI

{

    NSLog(@"已经销售%d 张票\n剩余 %d 张票\n当前销售窗口是：%@",saleTicketNum,curTicketNum,saleWindowName);

    showLable.text = [NSString stringWithFormat:@"已经销售%d 张票\n剩余 %d 张票\n当前销售窗口是：%@",saleTicketNum,curTicketNum,saleWindowName];

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

@end

多线程的使用实列-卖票系统

标签：

原文地址：http://blog.csdn.net/jzq_sir/article/details/48030997