iOS多线程开发小demo4，线程的同步问题

//  DYFViewController.m
//  623-05-线程同步问题
//
//  Created by dyf on 14-6-23.
//  Copyright (c) 2014年 ___FULLUSERNAME___. All rights reserved.
//

#import "DYFViewController.h"

@interface DYFViewController ()
@property (nonatomic, assign) int leftCount;

@property (nonatomic, strong) NSThread *thread0;
@property (nonatomic, strong) NSThread *thread1;
@property (nonatomic, strong) NSThread *thread2;

@end

@implementation DYFViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    
    // 默认有100张
    self.leftCount = 100;
    // 开启多条线程同时卖票
    self.thread0 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:@"000"];
    self.thread0.name = @"0000";
    // 优先级
    self.thread0.threadPriority = 1.0;
    
    self.thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:@"000"];
    self.thread1.name = @"1111";
    self.thread1.threadPriority = 0.0;
    
    self.thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:@"000"];
    self.thread2.name = @"2222";
    self.thread2.threadPriority = 0.0;
    
    
}

/**
 *  卖票
 */
- (void)saleTicket
{
//    NSLock *lock = [[NSLock alloc] init];
//    lock.tryLock
//    lock.lock
    
    while (1) {
    
        @synchronized(self){ // 开始枷锁
        
        // 1.先检查票数
        int count = [self leftCount];
        if (count > 0) {
            // 票数 - 1
            [self setLeftCount:(count - 1)];
            // 暂停
            [NSThread sleepForTimeInterval:0.0004];
            NSThread *currentT = [NSThread currentThread];
            NSLog(@"%@,-------%d", currentT.name, self.leftCount);
        }else
        {
            // 退出线程
            [NSThread exit];
        }
        } // 解锁
    }
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self.thread0 start];
    [self.thread1 start];
    [self.thread2 start];
}

@end