Thanks to both of you for the follow-up.
For my use, the class being final is probably ok.
Dave Reed
> On Jan 10, 2017, at 3:05 AM, Slava Pestov <spes...@apple.com> wrote:
>
>>
>> On Jan 9, 2017, at 11:59 PM, Pierre Monod-Broca via swift-users
>> <swift-users@swift.org> wrote:
>>
>> Hi again,
>>
>> You might want to look at Self requirement in protocols for exemple:
>> protocol P {
>> func items(/*...*/) -> [Self]
>> }
>> class C: P {
>> func items(/*...*/) -> [C] {
>> ...
>> }
>> }
>
> FWIW, this requires that ‘C’ is final. Otherwise, a subclass ‘D’ of ‘C’ won’t
> satisfy the requirement, because C.items() still returns a ‘C’ and not a ‘D’.
>
>>
>> However it might not always work as you expect.
>>
>> I can't say which is the better. Using associated type might be more
>> flexible.
>>
>> Pierre
>>
>>> Le 5 janv. 2017 à 21:10, davel...@mac.com a écrit :
>>>
>>> Yes, it does seem to work. I just wondered if there was a better way to do
>>> it. Perhaps by writing the method in a base class (but I couldn't get that
>>> to work) instead of using an extension. Then I could just inherit from that
>>> base class rather than needing to write:
>>>
>>> extension Event: DDRCoreData {
>>> typealias Entity = Event
>>> }
>>>
>>> in addition to class Event: NSManagedObject . . .
>>>
>>> Yes, I know in Xcode 8, that last part can now be written for you.
>>>
>>> Again, if this is the "right way to do it", I'm ok with that, I just
>>> wondered if there is a better way to do it.
>>>
>>> Thanks,
>>> Dave Reed
>>>
>>>
>>>> On Jan 5, 2017, at 2:35 PM, Pierre Monod-Broca
>>>> <pierremonodbr...@gmail.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> It looks that you have what you wanted because Event.Entity is an alias of
>>>> Event.
>>>>
>>>> Pierre
>>>>
>>>>> Le 5 janv. 2017 à 16:47, Dave Reed via swift-users
>>>>> <swift-users@swift.org> a écrit :
>>>>>
>>>>> Is there a way to make a static or class method specify the return type
>>>>> be the actual class it is called with?
>>>>>
>>>>> The example code below using protocols/extensions mostly works (the type
>>>>> is [Event.Entity] not [Event] but it seems to work.
>>>>>
>>>>> If I try to make DDRCoreData a base class and Event subclass it, I'm only
>>>>> able to get the return type to be [DDRCoreData], not [Event] when I call
>>>>> it with Event.items(in: moc)
>>>>>
>>>>> Here is the code that mostly works using protocols. Is there a better way
>>>>> to do this?
>>>>>
>>>>> protocol DDRCoreData {
>>>>> associatedtype Entity: NSManagedObject
>>>>>
>>>>> static func items(in context: NSManagedObjectContext, matching predicate:
>>>>> NSPredicate?, sortedBy sorters: [NSSortDescriptor]?) -> [Entity]
>>>>> }
>>>>>
>>>>> extension DDRCoreData {
>>>>> static func items(in context: NSManagedObjectContext, matching predicate:
>>>>> NSPredicate? = nil, sortedBy sorters: [NSSortDescriptor]? = nil) ->
>>>>> [Entity] {
>>>>> var items: [Entity] = []
>>>>> context.performAndWait {
>>>>> let fetchRequest: NSFetchRequest<Entity> = Entity.fetchRequest()
>>>>> as! NSFetchRequest<Entity>
>>>>> fetchRequest.predicate = predicate
>>>>> fetchRequest.sortDescriptors = sorters
>>>>> do {
>>>>> items = try fetchRequest.execute() as [Entity]
>>>>> } catch {
>>>>>
>>>>> }
>>>>> }
>>>>> return items
>>>>> }
>>>>> }
>>>>>
>>>>> @objc(Event)
>>>>> public class Event: NSManagedObject {
>>>>>
>>>>> }
>>>>>
>>>>> extension Event: DDRCoreData {
>>>>> typealias Entity = Event
>>>>> }
>>>>>
>>>>> // compiler says items is of type [Event.Entity]
>>>>> let items = Event.items(in: controller.managedObjectContext!)
>>>>>
>>>>> Thanks,
>>>>> Dave Reed
>>>>>
>>>>>
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>>>
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