All About Concurrency in Swift
Swift 3 introduces a new function to perform assertions on the current execution context, that allows to verify if a closure is being executed on the expected queue. We can build predicates using the three enum cases of
DispatchPredicate:.onQueue, to verify that we are on a specific queue,.notOnQueue, to verify the opposite and.onQueueAsBarrierto check if the current closure or work item are acting as a barrier on a queue.
Update (2017-06-04): John Sundell:
One common misconception about GCD is that “once you schedule a task it cannot be cancelled, you need to use the
OperationAPI for that”. While this used to be true, with iOS 8 & macOS 10.10DispatchWorkItemwas introduced, which provide this exact functionality in a very easy to use API.[…]
As you can see above, using
DispatchWorkItemis actually a lot simpler and nicer in Swift than having to use aTimerorOperation, thanks to trailing closure syntax and how well GCD imports into Swift. You don’t need@objcmarked methods, or#selector, it can all be done with closures.
