我可以使用GCD限制并发请求吗? [英] Can I limit concurrent requests using GCD?
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问题描述
我正在从数据库异步获取数据.有什么方法可以将并发请求限制为一个数字,但仍然执行其余请求?
I'm acquiring data from a database asynchronously. Is there any way I can limit the concurrent requests to a number, but still execute the rest?
我看到了使用NSOperation和NSOperationQueue的帖子 但这对我来说太复杂了. 还有其他方法吗? GCD可以实现吗?
I saw a post using NSOperation and NSOperationQueue but this is too complicated for me. Is there any other ways to do it? Can GCD achieve it?
推荐答案
类似以下内容:
...
//only make one of these obviously :) remaking it each time you dispatch_async wouldn't limit anything
dispatch_semaphore_t concurrencyLimitingSemaphore = dispatch_semaphore_create(limit);
...
//do this part once per task, for example in a loop
dispatch_semaphore_wait(concurrencyLimitingSemaphore, DISPATCH_TIME_FOREVER);
dispatch_async(someConcurrentQueue, ^{
/* work goes here */
dispatch_semaphore_signal(concurrencyLimitingSemaphore);
}
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