NSURLConnection and sendAsynchronousRequest:queue:completionHandler: - does the completion block run in the main thread

Question

If I use NSURLConnection with sendAsynchronousRequest:queue:completionHandler: , do I need to take any particular precautions inside the completion handler? Specifically, is sending asynchronously directly via NSURLConnection the same/similar as using dispatch_async in that the completion block would need to come back to the main thread to interact with the UI?

For example: after using dispatch_async to interact (maybe the wrong word) with the UI, the app must use performSelectorOnMainThread .

Is that a consideration at all with sendAsynchronousRequest:queue:completionHandler: ?

note: I have found similar questions, but not this specifically. eg, in Does NSURLConnection block the main thread? indiekiduk specifically states it is a new thread, albeit an internal one--I think that is flawed, since I thought it was just at the end of the run loop--but I am still learning and probably/possibly wrong.

Answer 1

The documentation for NSURLConnection states for the queue parameter to sendAsynchronousRequest:queue:completionHandler:

queue
The operation queue to which the handler block is dispatched when the request completes or > failed.

The block will execute on whichever thread the passed in queue was set up on.

Answer 2

NSURLConnection sendAsync是在AFAIK上的线程的RunLoop上调度的，所以在启动它的线程中调用该块