GCD vs PerformSelectorInBackground/performSelectorOnMainThread

问题描述

我是ios开发的新手.我有以下问题:

I am new in ios development. I have following questions:

1. 何时使用GCD(dispatch_group_async，dispatch_async(dispatch_get_main_queue()...)以及何时使用performSelectorInBackground/performSelectorOnMainThread?

2. 这两者之间有什么区别.

1. When we use GCD(dispatch_group_async, dispatch_async(dispatch_get_main_queue()...) and when we use performSelectorInBackground/performSelectorOnMainThread?

2. What's the differences between those two.

我知道当我们使用performSelectorInBackground时，我们会创建一个新的NSThread.但是当我们使用dispatch_group_async时不一样吗?因为如果我们创建一个以上的dispatch_group_async，则意味着我们需要在队列中提交多个以上的块.这些块可能在不同的队列上运行.因此，当我们创建一个以上的dispatch_group_async时，是否意味着我们创建了一个新线程? (因为块可能在不同的队列上运行)(我对NSThread和块队列感到困惑.....)

I know when we use performSelectorInBackground, we create a new NSThread. But isn't the same when we use dispatch_group_async? Because if we create more than one dispatch_group_async, it means we need to submit more than one blocks in queue. And those blocks might run on different queues. Therefore, when we create more than one dispatch_group_async, does it means we create a new thread? (because blocks may run on different queues) (I kind of confused about NSThread and block queue.....)

谢谢！

推荐答案

何时使用performSelectorInBackground:

从不.不要使用此方法.它产生无限数量的线程.甚至在GCD可用之前，这都是一种可怕的方法.

When to use performSelectorInBackground:

Never. Do not use this method. It spawns an unbounded number of threads. Even before GCD was available, this was a horrible method.

嗯……从不，只是因为不方便.这种方法没有什么大不了的.它不如dispatch_async()有用.

Meh… Never, but just because it's inconvenient. There's nothing deeply wrong with this method. It's just not as useful as dispatch_async().

GCD与旧的performSelector…方法(通常是NSThread)之间的区别在于，GCD为您管理线程池.通常，应避免在Cocoa中进行手动穿线.而是使用NSOperationQueue或GCD(dispatch方法).它们提供了更有用的队列抽象，而不是强迫您手动管理线程.

The difference between GCD and the old performSelector… methods (and NSThread in general) is that GCD manages a thread pool for you. In general, you should avoid manual threading in Cocoa. Instead, use NSOperationQueue or GCD (dispatch methods). They provide a more useful queue abstraction rather than forcing you to manually manage threads.

请务必阅读Apple的从线程迁移了解更多信息.

Be sure to read over Apple's Migrating Away from Threads for more info.

这篇关于GCD vs PerformSelectorInBackground/performSelectorOnMainThread的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！