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Bindings Problem
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Bindings Problem


  • Subject: Bindings Problem
  • From: John McLaughlin <email@hidden>
  • Date: Thu, 5 Jan 2006 15:27:20 -0800

 have a (Odd?) problem with bindings that is driving me crazy...

Let's say I have a class called 'A' with a member variable (NSString*)
called 'status'

If I bind a NSTextField to A.status all is good.... as I update my 'status'
variable programatically  it propogates to the UI and if I change the
NSTextField by 'typing into it' it propogates down to the 'status'
varible... so I know it's bound OK.

Now let's say my object 'A' contains a object 'B' and and now 'B' contains
the member variable (NSString*) called 'status'

If I bind my NSTextField to A.B.status I can 'type' into the NSTextField and
it properly propogates down to the 'status' member variable in 'B' (So I
know it's bound properly)

However If I programatically change 'B'  the UI never updates......


My work around is ugly right now.... I create getter and setter in 'A' for
the variable (getStatus, setStatus:(NSString*)) that's only job in life is
to set or query the 'B' object (I don't store it locally in A) and I post a
notification in the 'B' object when 'status' updates so that 'A' object can
catch it and perform [self setStatus:[self getStatus]] so that the UI
properly updates.

It works but it's sooooo ugly....

So my question is:

   1. Is this somehow expected behaviour (e.g. bindings only work one way
   for objects in objects)?
   2. Is there a way I can post a notification in 'B' that the bound
   value will notice something has changed? (thus avoiding making 'A' get
   involved)... E.G. is it documented anywhere what should get posted and
   could I throw this manually (via my code)
   3. ?? Anything else I should know

It's so frustrating because when bindings work they are tremendous but this
problem is really making them almost not worth it since I'm being forced to
write a lot of code to propoate everything to the 'A' object which is sort
of defeating the purpose....

Regards,

-John
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