Can a model key path binding access a super class property
Hi all,
I have two classes, one defining a few base properties, and another more
specific class inheriting from it. Example below:
@interface BBSBaseClass : NSObject {
NSString*aValue;
}
@property (readwrite, copy) NSString*aValue;
@end
@interface BBSMoreSpecific : BBSBaseClass {
NSString*anotherValue;
}
@property (readwrite, assign) NSString *anotherValue;
@end
In my window I have a NSTableView that is using an array controller to get
access to my data. The array controller is bound to an array of
BBSMoreSpecific classes.
The problem I am having is that all of my columns bound to the fields in the
BBSMoreSpecific class show their data, but those bound to those in the base
class do not. I am using a simple model key path of just the name of the ivar,
so aValue and anotherValue.
Can the bindings access the base class or can they only access values in the
class the array controller is directly connected to?
regards,
---
Grant Christensen
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Re: Can a model key path binding access a super class property
Grant Christensen mailto:gran...@bigpond.net.au wrote (Sunday,
January 17, 2010 6:53 AM +1000):
In my window I have a NSTableView that is using an array controller to get
access to my data. The array controller is bound to an array of
BBSMoreSpecific classes.
The problem I am having is that all of my columns bound to the fields in the
BBSMoreSpecific class show their data, but those bound to those in the base
class do not. I am using a simple model key path of just the name of the
ivar, so aValue and anotherValue.
Can the bindings access the base class or can they only access values in the
class the array controller is directly connected to?
Of course you can. This is a basic principle of object oriented
languages (unless there's scoping, but Objective-C doesn't
support that). You could verify this by using a key-value path
to access any of the object's NSObject properties, like -description.
I suspect that something else is wrong. Your simplistic example
appears to be valid, but it's obviously not the code you're
using. It time to hit the debugger
Since you've declared these as formal properties, KVO should be
accessing these properties via their accessor methods. One trick
is to override the base-class getter method in your subclass
like this:
@implementation BBSMoreSpecific
...
- (NSString*)aValue
{
NSString* value = [super aValue];
//NSLog(@%s returning '%@',__func__,value);
return value; // -- set breakpoint here
}
Now you can set a breakpoint or log every access to that
property. You shouldn't have any problem verifying if the
correct messages are being sent (or not), by whom, and then work
backwards from there.
--
James Bucanek
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[SOLVED]: Re: Can a model key path binding access a super class property
Thanks for the nudge in the right direction James... I went back to the
debugger and found an underlying problem with the two variables in the base
class that were not coming through. It as a mere coincidence that it was those
two in the base class, and I was not setting them correctly in the first place.
Always the simple answers :)
regards,
Grant
On 18/01/2010, at 3:04 AM, James Bucanek wrote:
Grant Christensen mailto:gran...@bigpond.net.au wrote (Sunday, January 17,
2010 6:53 AM +1000):
In my window I have a NSTableView that is using an array controller to get
access to my data. The array controller is bound to an array of
BBSMoreSpecific classes.
The problem I am having is that all of my columns bound to the fields in the
BBSMoreSpecific class show their data, but those bound to those in the base
class do not. I am using a simple model key path of just the name of the
ivar, so aValue and anotherValue.
Can the bindings access the base class or can they only access values in the
class the array controller is directly connected to?
Of course you can. This is a basic principle of object oriented languages
(unless there's scoping, but Objective-C doesn't support that). You could
verify this by using a key-value path to access any of the object's NSObject
properties, like -description.
I suspect that something else is wrong. Your simplistic example appears to be
valid, but it's obviously not the code you're using. It time to hit the
debugger
Since you've declared these as formal properties, KVO should be accessing
these properties via their accessor methods. One trick is to override the
base-class getter method in your subclass like this:
@implementation BBSMoreSpecific
...
- (NSString*)aValue
{
NSString* value = [super aValue];
//NSLog(@%s returning '%@',__func__,value);
return value; // -- set breakpoint here
}
Now you can set a breakpoint or log every access to that property. You
shouldn't have any problem verifying if the correct messages are being sent
(or not), by whom, and then work backwards from there.
--
James Bucanek
---
Grant Christensen
___
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