On Aug 22, 2009, at 5:47 PM, Quincey Morris wrote:
On Aug 22, 2009, at 16:16, Michael de Haan wrote:
..........or a fundamental misunderstanding.
Fundamental misunderstanding. :)
That figures!
I have a checkbox, which I wish to bind to an iVar in my model
( which is a windowController).
No, you don't bind anything to an ivar, you bind things to properties.
My lack of correct syntax...but your point is well taken.
What I am doing right now is creating an NSButton object in the
model, and "assuming" .....probably incorrectly, that by having the
correct getters/setters available ( eg state/setState etc) I can
bind the view's checkbox title, alternateTitle, status to the
NSButton in the model. That is not working for me. ("Cannot create
BOOL from object <NSButton: 0x19f6c0> of class NSButton").
Your NSButton object isn't *in* the model. It may be an outlet of
the window controller,
Correct
but that's a feature of the controller role, not of the data model
role, of the window controller. Bind *from* your view (the checkbox)
*to* properties of your data model.
OK...that certainly clarifies one thing....so, one **cannot** bind to
an object, but to that object's properties? (Hence the error when I
tried that).
Specifically, in IB, you'll bind the NSButton's "value" binding to
the "state" property of File's Owner (your window controller).
Is this my error, or do I need to create an iVar for each of the
button elements I wish to bind to?
If you want to bind the "title" and "alternateTitle" bindings too
(not that I'd recommend it -- the whole point of a checkbox is that
the on/off state is shown by the checkmark, not by the text), then
you must create properties of your window controller to bind to.
These will be NSString* properties.
Perhaps I am not using the checkbox correctly, but I wish the label to
illustrate that checked represents one type of unit ( eg pounds) and
unchecked another ( eg kilograms).
( But, mainly I am trying to use my "Hillegass" knowledge as I work my
way through his book. Just reading without trying to use it is pretty
pointless to me and gives one a false sense of understanding...just
IMHO. Plus making little apps that I use at work gives a sense of
fulfillment.)
This issue, of ensuring correct propagation of your properties, is
called "KVO-compliance", which you may have already come across.
Quincey, I **hope** my level of question did not imply that I was "KVO-
ignorant" :-)
Thanks ...will try what you say.
Michael.
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