问题
I think GCD is todo with asynchronous events, but specifically, I am not sure what type of events/where GCD comes in useful, apart from the obvious web requests.
Could you explain what GCD is and where it should/shouldn't be used?
回答1:
I strongly suggest you to read the chapter called "Dispatch Queues" in Apple's Concurrency Programming Guide. It is an excellent document and clearly depicts the differences with standard multi-thread programming. This reading (will not take you more than 10 minutes to read, quite more to digest of course!) is quite better than any other word I can put here! link to apple developer site
来源：https://stackoverflow.com/questions/6539656/what-exactly-is-gcd-and-where-should-it-be-used