When Would Anyone Want To Use NSThreads over the GCD?

Question

Are there any cases when anyone would want to use raw NSThreads instead of GCD for concurrency? I love the GCD, but I want to know if I will need to use NSThreads for Cocoa/Cocoa-Touch eventually.

Zink

Answer 1

i use pthreads for control, good performance, and portability. sometimes, you might opt to use NSThread for the extra NSObject interfacing it offers.

there are a few lower level interfaces where you need to coordinate threads with the APIs you use (e.g. realtime I/O or rendering). sometimes you have flexibility regarding the thread you use, sometimes it is convenient to use NSThread in this situation so you can easily use CF or NS run loops with these interfaces. So the run loop parameter you set up on your thread is likely of more interest to the API than the thread itself. in these cases, GCD may not necessarily be an alternative.

but… most devs won't need to drop to these levels often.

Zane

Answer 2

You should essentially almost never need to use the NSThread/pthread APIs directly on OS X or iOS. On other platforms, possibly yes (though GCD is becoming more widely ported to *BSD, Linux and even Windows - see Wikipedia page for Grand Central Dispatch), but on Apple OS platforms you're almost always going to get a better result by allowing the system to do thread lifecycle management for you. The only case where you might conceivably want to do your own thread management are in highly real-time scenarios where you need to manage thread priorities and have direct control over thread latency by balancing the amount of work each thread is doing by hand.

Toponym

Answer 3

There may be some special situations where you have to do something strange that cannot be done with GCD. But anything that you can do with GCD you should do it that way (GCD and threads are not mutually exclusive, if you need to actually use a thread you need not change any of the GCD stuff you already have).

Not sure however what the case would be. Maybe if you need to setup a secondary specialized RunLoop (not sure if it can be done with GCD but surely it can with a thread). Or there may be some other special case I cannot figure at the moment.

Aprylapse