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