> On 18 Apr 2017, at 12:01 am, Rod Brown via swift-users > <[email protected]> wrote: > > Hi Rick, > > Unfortunately, that is the case. You cannot subclass a Swift class (even if > it is a subclass of NSObject and available to the Objective-C runtime) > because of deliberate limitations baked into Obj-C to block subclassing Swift > classes in Obj-C code.
Sorry, correction here: You cannot subclass a Swift class *in Objective C*. > I believe the reason for this limitation is that Swift includes features that > cannot be utilised in Obj-C and therefore subclasses would be restricted and > would get undefined behaviour when implementing methods that cannot cross > into Obj-C. > > If Apple were to allow Obj-C -> Swift -> Obj-C subclassing, then it would be > on a limited basis. Some methods wouldn’t do the same thing in Swift as they > would in Obj-C selectors, and you could theoretically declare conflicting > methods in your subclass that would have different actions depending on > whether you were addressing the class in Swift and Obj-C. Additionally, the > Swift Compiler couldn’t see beyond the Swift barrier and therefore may make > optimisations that would break your Obj-C subclasses. > > While I understand the frustration behind this, both in personal projects and > philosophically, I think that this is unfortunately the better of the two > options. > > - Rod _______________________________________________ swift-users mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-users
