Thanks, I didn't even think of that, but yeah, it would be easier. Still, I'd
like to know how to properly write a value transformer in Swift.
On May 12, 2015, at 5:38 PM, Quincey Morris
<quinceymor...@rivergatesoftware.com> wrote:
> On May 12, 2015, at 14:29 , William Squires <wsqui...@satx.rr.com> wrote:
>>
>> class IsNotEmptyTransformer : NSValueTransformer
>> {
>> }
>>
>> but the example in the documentation is in ObjC, not Swift, and refers to
>> id, not to "Bool"s or "String"s. Hints, anyone?
>
> Using a value transformer at all seems like a poor choice, and using one in
> Swift seems even less desirable.
>
> If you are intent on using one, you’ll need to ask a more specific question.
> What ‘id’ are you referring to? If you’re talking about the transformed
> value, then you have to use an object — specifically NSNumber to represent a
> boolean value. IOW, for your use case, the transformer would transform
> between NSNumber and NSString.
>
> Surely it would be far easier, though, to do what you would do in a modern
> Obj-C app: use a derived property. Add a new property to the window
> controller:
>
> class MyWindowController : NSWindowController
> {
> dynamic var message: String
> dynamic var messageIsEmpty: Bool {return String == “”}
>
> and bind the button’s Enabled binding to the “messageIsEmpty” property.
> That’s not quite all, though, because as it stands, “messageIsEmpty” isn’t
> KVO-compliant, so you also need to add:
>
> static var keyPathsForValuesAffectingMessageIsEmpty: NSSet {return NSSet
> (object: "messageIsEmpty”)}
>
> (All code written in Mail, not tested.)
>
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