> 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
>>>>
>>>>
>>>> _______________________________________________
>>>> swift-users mailing list
>>>> swift-users@swift.org
>>>> https://lists.swift.org/mailman/listinfo/swift-users
>>
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