有没有办法无限期地暂停NSTHread并让它从另一个线程恢复？

Question

似乎这些是让NSThread进入睡眠状态的唯一方法

* sleepForTimeInterval:

* sleepUntilDate:

我要问的是不好的做法吗？

Answer 1

你想让你的线程停止,直到某个其他线程告诉它再次启动？如果是这样,您可以使用NSConditionLock.NSConditionLock类似于条件变量.它有几个基本方法,lockWhenCondition和unlockWithCondition,以及lock.一个典型的用法是让你的后台线程在条件锁上等待"lockWhenCondition:",并在前台线程中设置条件,这会导致后台线程被唤醒.条件是一个简单的整数,通常是枚举.

这是一个例子:

enum {
    kWorkTodo = 1,
    kNoWorkTodo = 0
}

- (id)init {
    if ((self = [super init])) {
        theConditionLock = [[NSCoditionLock alloc] initWithCondition: kNoWorkTodo];
        workItems = [[NSMutableArray alloc] init];
    }
}

- (void)startDoingWork {
    [NSThread detachNewThreadSelector:@selector(doBackgroundWork) toTarget:self withObject:nil];
}

- (void)doBackgroundWork:(id)arg {
    while (YES) {
        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
        NSArray *items = nil;
        [theConditionLock lockWhenCondition:kWorkTodo]; // Wait until there is work to do
        items = [NSArray arrayWithArray:workItems]
        [workItems removeAllObjects];
        [theConditionLock unlockWithCondition:kNoWorkTodo];
        for(id item in items) {
            // Do some work on item.
        }
        [pool drain];
    }
}

- (void)notifyBackgroundThreadAboutNewWork {
    [theConditionLock lock];
    [workItems addObject:/* some unit of work */];
    [theConditionLock unlockWithCondition:kWorkTodo];
}

在这个例子中,当调用startDoingWork时,doBackgroundWork:将在后台线程上启动,但随后停止,因为没有任何工作要做.一旦调用了notifyBackgroundThreadAboutNewWork,那么doBackgroundWork:将启动并处理新工作,然后返回休眠状态等待新工作可用,这将在下次调用notifyBackgroundThreadAboutNewWork时发生.