Objective c 中的等待和通知等效项

在Objective-C中，等待和通知是一种常见的编程模式，用于在多线程环境中进行线程间的同步和通信。这种模式可以确保线程之间的顺序执行，并且能够有效地避免竞态条件和死锁等问题。在本文中，我们将讨论Objective-C中的等待和通知等效项，并提供一些实际的案例代码来帮助读者更好地理解这个概念。

objective-c
#import 
dispatch_semaphore_t producerSemaphore;
dispatch_semaphore_t consumerSemaphore;
NSMutableArray *buffer;
NSInteger bufferLimit = 10;
NSInteger producerItemCount = 0;
void producerThread() {
    while (producerItemCount < bufferLimit) {
        // 生产物品
        NSString *item = [NSString stringWithFormat:@"Item %ld", (long)producerItemCount];
        
        // 等待缓冲区有足够的空间
        dispatch_semaphore_wait(producerSemaphore, DISPATCH_TIME_FOREVER);
        
        // 将物品放入缓冲区
        [buffer addObject:item];
        NSLog(@"Producer: %@ added to buffer", item);
        
        // 通知消费者线程有新的物品可供消费
        dispatch_semaphore_signal(consumerSemaphore);
        
        producerItemCount++;
        [NSThread sleepForTimeInterval:0.5];
    }
}
void consumerThread() {
    while (producerItemCount < bufferLimit || [buffer count] > 0) {
        // 等待有物品可供消费
        dispatch_semaphore_wait(consumerSemaphore, DISPATCH_TIME_FOREVER);
        
        // 从缓冲区取出物品进行消费
        NSString *item = [buffer firstObject];
        [buffer removeObjectAtIndex:0];
        NSLog(@"Consumer: %@ consumed", item);
        
        // 通知生产者线程有空位可供生产
        dispatch_semaphore_signal(producerSemaphore);
        
        [NSThread sleepForTimeInterval:1.0];
    }
}
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        producerSemaphore = dispatch_semaphore_create(bufferLimit);
        consumerSemaphore = dispatch_semaphore_create(0);
        buffer = [NSMutableArray array];
        
        NSThread *producer = [[NSThread alloc] initWithTarget:producerThread selector:@selector(invoke) object:nil];
        NSThread *consumer = [[NSThread alloc] initWithTarget:consumerThread selector:@selector(invoke) object:nil];
        
        [producer start];
        [consumer start];
        
        [producer join];
        [consumer join];
    }
    return 0;
}