moc is declared inside the view controller class, which is a subclass of NSViewController which is an Objective-C class. So I believe the scope is @objc
In any case, I tried to prefix the declaration with “@objc”, but this is has no visible effect. That being said, prefixing its declaration with “dynamic” sort of fixes the problem: Interface Builder still complains as described, but the program now works fine at runtime. I have a hard time understanding clearly why: for bindings to work, the bound properties need to be KVO-compliant. But wouldn’t the @objc scope already do that? What is the exact effect of the dynamic annotation? JD PS: I made a zip archive of the project available at http://dl.free.fr/pWkoKQLOc <http://dl.free.fr/pWkoKQLOc>. There is also an equivalent Objective-C project that works fine. > On 17 Jan 2017, at 17:43, David Sweeris <daveswee...@mac.com > <mailto:daveswee...@mac.com>> wrote: > > Is `moc` declared in a non-"@objc" scope? I think there's a > "@IBsomethingerather" that you have to put in front of those to let Interface > Builder see them or something. Sorry I can't be more definitive, but I'm not > in front of my computer and can't double-check. > > HTH > - Dave Sweeris > > Sent from my iPhone > >> On Jan 16, 2017, at 10:11, Jean-Denis Muys via swift-users >> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote: >> >> Hi, >> >> I am exploring the use of Swift for a Mac Cocoa application - using Xcode >> 8.2.1, and it seems I hit a roadblock regarding Cocoa bindings. >> >> In this toy Core Data document-based project, I added an NSArrayController >> in the StoryBoard. I need to bind it a NSManagedObjectContext so that my >> user interface works by itself. I followed the solution outlined in >> Technical Q&A QA1871 >> (https://developer.apple.com/library/content/qa/qa1871/_index.html >> <https://developer.apple.com/library/content/qa/qa1871/_index.html>). >> >> So I want to add a property of type ManagedObjectContext to my >> ViewController class. >> >> I naturally declared it as an optional: >> >> var moc: ManagedObjectContext? >> >> But when I enter the property name in the bindings inspector of >> InterfaceBuilder, it complains: there is a red exclamation mark, and >> hovering over it pops up this error message: >> >> “The Managed Object Context binding expects to be bound to an object of type >> NSObject, but mac is of type ManagedObjectContext?” >> >> And it fails at run time too. >> >> changing the type to ManagedObjectContext! doesn’t help: IB complains in >> exactly the same way. >> >> changing the type to a non optional ManagedObjectContext silences the IB >> error, but now my ViewController class doesn’t compile anymore. The error I >> get is: >> >> class ViewController has no initialiser >> >> I completely understand this error message. And I can add an initialiser. >> But I get this new error message: >> >> property ‘self.moc’ not initialised at super.init call. >> >> I understand that one too, but what can I do? At initialiser-time, the >> managedObjectContext is not yet known. In Objective-C I would set it to nil, >> which I cannot do since the property is not an optional any more. >> >> Do I really need to allocate a dummy sentinel ManagedObjectContext, just to >> make the compiler happy? >> >> This would be ugly as hell, far worse than the nil value we use in >> Objective-C. Swift in that case, would not be safer, but less safe than >> Obj-C. >> >> I find this idea repulsive. Or did I miss something? >> >> Or is Swift fundamentally incompatible with Cocoa bindings? That would be a >> pity too. >> >> Thanks, >> >> Jean-Denis >> >> >> _______________________________________________ >> swift-users mailing list >> swift-users@swift.org <mailto:swift-users@swift.org> >> https://lists.swift.org/mailman/listinfo/swift-users
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