Re: Binding
Re: Binding
- Subject: Re: Binding
- From: Ken Thomases <email@hidden>
- Date: Tue, 14 Apr 2009 14:14:13 -0500
On Apr 14, 2009, at 11:05 AM, Livio Isaia wrote:
Is it possible to connect a variable of an object I created to an
NSArrayController variable?
To be clear: bindings deal with properties, not variables. I don't
necessarily mean "declared properties" using @property, but properties
in the Key-Value Coding and Key-Value Observing sense.
A property is embodied in the instance methods of your class. If a
property is backed by an instance variable, that's an implementation
detail. The instance variable is not the property. The methods are.
(Yes, KVC can access instance variables directly, if you let it. You
shouldn't let it. That is, you should override
+accessInstanceVariablesDirectly to return NO for all of your
classes. Allowing KVC to access instance variables directly violates
encapsulation and will cause trouble.)
I mean:
I have a NSWindowController "MyWindowController" which is also the
nib file's owner type class.
And in the nib you've set the class of File's Owner to
MyWindowController?
In the nib file I created an NSArrayController "MyArrayController"
connected with a NSTableView.
"MyWindowController" has a variable "seletedItem" and a method
(void)setSelectedItem:(NSNumber *)value.
It should also have a -selectedItem method -- the getter for the
property.
How can I bind "selectedItem" to a "MyArrayController"'s attribute
(e.g selection.item)? And is it possible to do it in
InterfaceBuilder (the MyWindowController's bindings Inspector window
is just blank)?
It sounds a bit like you're thinking of this backwards. You don't
bind from File's Owner to the array controller. You bind from the
array controller to File's Owner.
In general, you should only use (or seek to use) bindings that are
defined for the classes you're using. For example, the bindings
defined for the classes in Cocoa are listed in the Cocoa Bindings
Reference <http://developer.apple.com/documentation/Cocoa/Reference/CocoaBindingsRef/
>. As you can see there's a finite list of classes for which
bindings are defined. If you use third-party classes which provide
bindings, they should be similarly documented.
Now, NSWindowController does not define any bindings. Likewise, you
have presumably not defined any bindings for MyWindowController, and I
wouldn't expect you to, based on the typical role of a window
controller. Usually, only views and mediating controllers provide
bindings. Coordinating controllers and models don't. Window
controllers are coordinating controllers.
I'm not sure what you're trying to achieve when you mention a key path
of "selection.item" on the array controller. What are you trying to
achieve?
Regards,
Ken
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| | >Binding (From: Livio Isaia <email@hidden>) |