IOS多线程（NSThread）

1.创建方法

使用NSThread创建线程主要有两个个方法，分别如下

1. NSThread* myThread = [[NSThread alloc] initWithTarget:self   selector:@selector(doSomething:) object:nil];

   [myThread start];

2. [NSThread detachNewThreadSelector:@selector(doSomething:) toTarget:self withObject:nil];

 

这两种方式的区别在于：

 

前一种方式尽管alloc了一个新Thread，但需要手动调用start方法来启动线程。这点与Java创建线程的方式相似。第二种方式，与上述做法1使用NSObject的类方法performSelectorInBackground:withObject:是一样的；第二种方式的可以在start真正创建线程之前对其进行设置，比如设置线程的优先级。第二种调用就会立即创建一个线程并执行selector方法。

使用NSThread创建线程时，要在执行的方法中自行管理内存，否则会有内存溢出警告。

- （void）doSomething:（id）sender

{

 

  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

 

  

 

   [pool release];

 

}

2.线程间的通讯

与主线程通讯

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

与指定的线程通讯

 [viewDelegate performSelector:@selector(someMethod)

                                 onThread:[NSThread mainThread]
                               withObject:nil
                            waitUntilDone:NO]

3.线程同步
线程同步主要用
NSCondition 和 NSLock

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    
    tickets = 100;
    count = 0;
    theLock = [[NSLock alloc] init];
    // 锁对象
    ticketsCondition = [[NSCondition alloc] init];
    ticketsThreadone = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
    [ticketsThreadone setName:@"Thread-1"];
    [ticketsThreadone start];
    
    ticketsThreadtwo = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];
    [ticketsThreadtwo setName:@"Thread-2"];
    [ticketsThreadtwo start];
    
    NSThread *ticketsThreadthree = [[NSThread alloc] initWithTarget:self selector:@selector(run3) object:nil];
    [ticketsThreadthree setName:@"Thread-3"];
    [ticketsThreadthree start];
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.

    [self.window makeKeyAndVisible];
    return YES;
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    return YES;
}


-(void)run3
{
    while (YES) {
        [ticketsCondition lock];
        [NSThread sleepForTimeInterval:3];
        [ticketsCondition signal];
        [ticketsCondition unlock];
    }
}

- (void)run
{
    while (TRUE) {
        // 上锁
        [ticketsCondition lock];
        [ticketsCondition wait];
        [theLock lock];
        if(tickets >= 0){
            [NSThread sleepForTimeInterval:0.09];
            count = 100 - tickets;
            NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);
            tickets--;
        }else{
            break;
        }
        [theLock unlock];
        [ticketsCondition unlock];
    }
}