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NSValueTransformer Loop
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NSValueTransformer Loop


  • Subject: NSValueTransformer Loop
  • From: "Gerriet M. Denkmann" <email@hidden>
  • Date: Sat, 3 Oct 2009 13:27:35 +0700

I have an NSStepper with maxValue bound to myArray.@count, minValue fixed at 1.
value bound to myArrayController selectionIndex and a PlusOneTransformer.


Works fine.

Also an NSTextField with value bound to myArrayController selectionIndex and a PlusOneTransformer.

Looks also ok.

But when I enter a number into this NSTextField reverseTransformedValue: of my PlusOneTransformer get called an infinite number of times (with the same argument) until the program crashes because at about 65000 calls the stack gets corrupted.

Here is my PlusOneTransformer:

+ (Class)transformedValueClass;
{
    return [NSNumber class];
}

+ (BOOL)allowsReverseTransformation;
{
    return YES;
}

- (id)transformedValue:(id)value;
{
 	NSUInteger a = [ value unsignedIntegerValue ];
	NSNumber *dd = [ NSNumber numberWithUnsignedInteger: a + 1 ];
	return dd ;
}

- (id)reverseTransformedValue:(id)value;
{
	NSUInteger a = [ value unsignedIntegerValue ];
	if ( a > 0 ) a--;
	NSNumber *dd = [ NSNumber numberWithUnsignedInteger: a ];
	return dd ;
}

What am I doing wrong?
(Adding a number formatter to the text field did not change anything)
I also tried to bind the max value of the stepper to @count - 1 but IB told me not to use "-".


Kind regards,

Gerriet.

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