ios - Will a Serial DispatchQueue wait if a task spawns a different thread

Question

Serial dispatch queues will execute their tasks one at a time. But what if I have task1 and task2 in the queue. task1 one starts execution and calls a function with a completion block (which I assume will use a different thread to execute). At this point, I believe task1 will exit, even though the completion block has not yet been called. Is it a possibility that task2 will start executing before the completion block from task 1 is executed?

Answer 1

是的。在正常情况下，这正是会发生的事情。

如果您想等待某事完成后再继续，请研究DispatchGroup。