Binding chicken and egg problem
Binding chicken and egg problem
- Subject: Binding chicken and egg problem
- From: Adrian Ruigrok <email@hidden>
- Date: Thu, 29 Sep 2005 11:09:57 -0700
I have a view displaying objects. You can think of them like graphic
objects: Circles and Squares.
I have a view inspecting the value of those objects. Radius for the
circle, width for the square. This is a vast simplification but it
illustrates the problem:
The inspector is different for a circle and a square. They have
different values. Each of the objects has its own subview for
inspecting its values and I swap that subview in and out depending no
what object is selected. I have an arrayController watching what is
selected. I have bound my custom controller's className to the kind
of object being inspected. Each inspector view also has its own
arrayController so I can tie up the fields in IB. I attach the
inspectors array controller in code when the appropriate object needs
to be inspected. When a circle is selected I remove whatever
inspector is there and add the subView with the circle inspector and
tie up its arrayController. In that subview the text field for the
radius is bound to the selection.radius.
However I have a timing problem. If I put up the circle inspector
when it is selected, then the bindings fail if the array controller
has not updated still thinks it is looking at the square. I have even
created my own arrayController and overridden willChange and
didChange hoping it went something like:
willChange:objectClass
willChange:selection
do all the changes
didChange:objectClass
didChange:selection
But it seems to do them all in batches
willChange:objectClass
setObjectClass
didChange:objectClass
willChange:selection
setSelectedIndexes
didChange:selection
... or something like that.
So how do I resolve the dependancy. I need to be informed before any
changes happen to the selectionIndexes so I an remove the bindings
from the arrayController for the current inspector View. Then after
the selection change has been completed I need to know so I can tie
up the array Controller for the now selected object to the documents
content and selection.
Hope this makes sense!
Thanks,
Adrian
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