有没有办法暂停一个NSTHread无限期，并从另一个线程恢复？

问题描述

似乎这些是使NSThread休眠的唯一方法

Seems these are the only methods to put a NSThread to sleep

* sleepForTimeInterval:

* sleepUntilDate:

这是不好的做法我要求吗？

Would it be bad practice what I am asking?

推荐答案

你想让你的线程停止，直到某些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，并锁定。一个典型的用法是让你的后台线程等待条件锁定lockWhenCondition：，并在你的前台线程设置条件，这导致后台线程被唤醒。条件是一个简单的整数，通常是枚举。

Do you want your thread to just stop until some other thread tells it to start up again? If so, you could use an NSConditionLock. An NSConditionLock is similar to a condition variable. It has a couple of basic methods, lockWhenCondition, and unlockWithCondition, and lock. A typical usage is to have your background thread waiting on the condition lock with "lockWhenCondition:", and the in you foreground thread to set the condition, which causes the background thread to wake up. The condition is a simple integer, usually an enumeration.

这里有一个例子：

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startDoingWork被调用doBackgroundWork：将会在后台线程，但随后停止，因为没有任何工作要做。一旦notifyBackgroundThreadAboutNewWork被调用，然后doBackgroundWork：将启动并处理新的工作，然后回到睡眠等待新的工作可用，这将发生在下一次notifyBackgroundThreadAboutNewWork被调用。

In this example, when startDoingWork is called doBackgroundWork: will start on a background thread, but then stop because there isn't any work to do. Once notifyBackgroundThreadAboutNewWork is called, then doBackgroundWork: will fire up and process the new work, and then go back to sleep waiting for new work to be available, which will happen the next time notifyBackgroundThreadAboutNewWork is called.

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