> Le 8 avr. 2016 à 14:47, Jonathan Hull via swift-evolution > <[email protected]> a écrit : > > Interesting proposal, but I wanted to mention a couple of potential issues > off the top of my head. I know when I was using optional requirements in > Objective C, I would often use the presence/lack of the method (not just > whether it returned nil) in the logic of my program. I used the presence of > a method as a way for the implementor of a delegate to naturally communicate > whether they wanted a more advanced feature. The absence of the method > itself is information which can be utilized, not just whether it returns nil, > and I believe that is part of what people are asking for when they say they > want optional methods in Swift. >
Couldn’t agree more. An telling example is NSFetchedResultsControllerDelegate.controller(_:didChangeObject:atIndexPath:forChangeType:newIndexPath:). When this method is not implemented, the NSFetchedResultsController does not have to perform the heavy computations of individual changes in a Core Data fetch request, since nobody is listening to them. In today’s Swift, this lazy behavior requires an extra configuration flag. Gwendal Roué
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