NSValueTransformer for NSPopupButton on CoreData integer attribute - objective-c

Question

I have a CoreData/SQLite app with an NSPopupButton presenting the possible values for some entity attribute (an integer). It automatically shows the attribute value in the database. The user must be able to assign another value so my code generates an array of all possible values on start-up. In my XIB, I have a NSObject for the button and an NSArrayController for the possible values. Bindings are done and everything works fine.
Of course, using only numbers is not clear for the user, so I created a value transformer to replace numbers by words on the popup button: 1=>Red, 2=>Green, 3=>Blue.
The problem is that only the selected Popup item is replaced by a word. And when I choose another value with the Popup button to modify the entity attribute, it doesn't save it. I see it by selecting another object in the TableView then coming back to the modified one and the Popup will indicate NoValue.
I don't understand why. Thank you for your help.
Here is the code of the header file "ColorOption.h":
#import <Foundation/Foundation.h>
#interface ColorOption : NSArrayController {
IBOutlet NSPopUpButton *colorPopup;
NSArray *theNumbers;
}
#property (retain) NSPopUpButton *colorPopup;
#property (readwrite, copy) NSArray *theNumbers;
#end
#interface StatusTransformer : NSValueTransformer {
}
#end
Here is the code of the implementation file "ColorOption.m":
#import "ColorOption.h"
#implementation ColorOption
#synthesize colorPopup;
#synthesize theNumbers;
-(void)awakeFromNib {
[self setTheNumbers:[NSArray arrayWithObjects:[NSNumber numberWithInt:1],[NSNumber numberWithInt:2],[NSNumber numberWithInt:3],nil]];
StatusTransformer *statusTrans = [[[StatusTransformer alloc] init] autorelease];
[NSValueTransformer setValueTransformer:statusTrans forName:#"StatusTransformer"];
}
#end
#implementation StatusTransformer
+ (Class)transformedValueClass { return [NSString class]; }
+ (BOOL)allowsReverseTransformation { return YES; }
- (id)transformedValue:(id)value {
switch ([value intValue]) {
case 1:
return #"Red";
break;
case 2:
return #"Green";
break;
case 3:
return #"Blue";
break;
default:
return #"";
break;
}
}
-(id)reverseTransformedValue:(id)value {
if ([#"Red" isEqualToString:value]) return [NSNumber numberWithInt:1];
if ([#"Green" isEqualToString:value]) return [NSNumber numberWithInt:2];
if ([#"Blue" isEqualToString:value]) return [NSNumber numberWithInt:3];
return nil;
}
#end

Answer 1

I'm reviewing my questions and see that this one has been left unanswered. However in the meantime I had found the answer which I'll post now so it may help others.
The mistake I did was to define the array of integer values while what I should have done is to define the array of words populating the popup button. Here is the full solution:
Header file :
#import <Cocoa/Cocoa.h>
#interface ColorOption : NSArrayController {
IBOutlet NSPopUpButton *colorPopup;
NSArray *theNames;
}
#property (strong) NSPopUpButton *colorPopup;
#property (readwrite, copy) NSArray *theNames;
#end
#interface StatusTransformer : NSValueTransformer {
}
#end
Implementation file
#import "ColorOption.h"
#implementation ColorOption
#synthesize colorPopup = _colorPopup;
#synthesize theNames = _theNames;
-(void)awakeFromNib {
[self setTheNames:[NSArray arrayWithObjects:[NSString stringWithFormat:#"Red"],[NSString stringWithFormat:#"Green"],[NSString stringWithFormat:#"Blue"],nil]];
StatusTransformer *statusTrans = [[[StatusTransformer alloc] init] autorelease];
[NSValueTransformer setValueTransformer:statusTrans forName:#"StatusTransformer"];
}
#end
#implementation StatusTransformer
+ (Class)transformedValueClass {
return [NSString class];
}
+ (BOOL)allowsReverseTransformation {
return YES;
}
- (id)transformedValue:(id)value {
switch ([value intValue]) {
case 1: {
return #"Red";
break;
}
case 2: {
return #"Green";
break;
}
case 3: {
return #"Blue";
break;
}
default: {
return nil;
break;
}
}
}
-(id)reverseTransformedValue:(id)value {
if ([#"Red" isEqualToString:value]) return [NSNumber numberWithInt:1];
if ([#"Green" isEqualToString:value]) return [NSNumber numberWithInt:2];
if ([#"Blue" isEqualToString:value]) return [NSNumber numberWithInt:3];
return nil;
}
#end
Now in the bindings inspector of Xcode, the value transformer must be applied to "Content Values" and "Selected Object" for the popup button.