Re: Bindings + contents of an array. No dice, for newb.

FROM : Shamyl Zakariya
DATE : Wed Apr 04 19:26:42 2007

It worked!

Thank you Mike, I really appreciate this. I've been writing Cocoa 
code since late 2002, but most of my work is graphics/physics written 
in C++ so my usage of Cocoa has been entirely of the old-school pre-
bindings nature ( Objective-C++ GUI atop a C++ core ).

Bindings seem completely orthogonal to how I've done GUI programming 
traditionally; I have a lot of re-education to go through. In fact, 
my greatest problem is that I don't even know how to *ask* a bindings 
question. There's a lot of new terminology I'm going to have to grok 
to be able to effectively ask questions here.

Thanks again,

<email_removed>
   In the same episode, the scientist suggests that the
   debigulation can only be reversed by a rebigulator.
       -- wikipedia


On Apr 4, 2007, at 10:21 AM, Mike Abdullah wrote:

> Hi Shamyl, having seen your screenshots, I see what the issue is.
>
> You are correctly observing the array itself so that KVO 
> notifications get sent that an object has been added or removed 
> from the array.  However, notice this method:
>
> [self setKeys:
>         [NSArray arrayWithObjects:
>             @"values",
>             @"values.value",
>             nil]
>         triggerChangeNotificationsForDependentKey: @"output"];
>
> It's "keys" not "keyPaths" , so you can't have the @"values.value" 
> work correctly.
>
> What I suggest you do instead, is bind your text field to 
> values.value.  Calling [-valueForKeyPath: @"values.value"] wo;; 
> return an NSArray of NSStrings.
>
> You want to add these strings together, so write an 
> NSValueTransformer whose -transformedValue: method looks something 
> like this:
>
> - (id)transformedValue:(id)value
> {
>     return [value componentsJoinedByString:@", "];
> }
>
> And use that as the value transformer for your new binding.  If you 
> post a sample project, I'll happily mod it so you can see.
>
> Mike.