Cocoa NSTextField NSNumberFormatter and delegate - xcode

Question

I'm making a NSTextField that has the following characteristics:
1) allows integer values only (0-9)
2) is 1 or 2 digits long
3) min of 1, max of 99
4) if 0 is entered, the value should change back to 1
5) if delete is pressed and the cell is completely emptied, the value should change to 1 and be automatically selected (hi-lighted) so that the user can simply type a new value
I'm able to get this behavior by creating a custom formatter and a delegate, but I want to implement this solely in the custom formatter (to keep things "simple" I suppose).
Here's the code I have:
In the delegate file:
- (void)controlTextDidChange:(NSNotification *)aNotification
{
if ([[txtfldSaveDuration stringValue] length]==0) {
[txtfldSaveDuration setStringValue:#"1"];
}
if ([[txtfldSaveDuration stringValue] isEqualToString:#"0"]) {
[txtfldSaveDuration setStringValue:#"1"];
}
}
in the custom formatter file:
#implementation OnlyIntegerValueFormatter
- (BOOL)isPartialStringValid:(NSString*)partialString newEditingString: (NSString**)newString errorDescription:(NSString**)error
{
// necessary otherwise can't delete (to select) the first character
if([partialString length] == 0) {
return YES;
}
// two integer max length (99)
if([partialString length] > 2) {
return NO;
}
// integers only
NSScanner* scanner = [NSScanner scannerWithString:partialString];
if(!([scanner scanInt:0] && [scanner isAtEnd])) {
NSBeep();
return NO;
}
return YES;
}
#end
How can I simplify this?

Answer 1

If you implement -isPartialStringValid:proposedSelectedRange:originalString:originalSelectedRange:errorDescription: instead, you get much more control, including over the resultant selected range.
Probably something like:
- (BOOL)isPartialStringValid:(NSString **)partialStringPtr
proposedSelectedRange:(NSRangePointer)proposedSelRangePtr
originalString:(NSString *)origString
originalSelectedRange:(NSRange)origSelRange
errorDescription:(NSString **)error
{
if ([*partialStringPtr length] == 0)
{
*partialStringPtr = #"1";
*proposedSelRangePtr = NSMakeRange(0, [*partialStringPtr length]);
return NO;
}
// two integer max length (99)
if ([*partialStringPtr length] > 2)
{
NSRange changed = NSMakeRange(origSelRange.location, [*partialStringPtr length] - (origString.length - origSelRange.length));
NSRange excess;
excess.length = [*partialStringPtr length] - 2;
excess.location = changed.location + (changed.length - excess.length);
*partialStringPtr = [*partialStringPtr stringByReplacingCharactersInRange:excess withString:#""];
*proposedSelRangePtr = NSMakeRange(excess.location, 0);
return NO;
}
// integers only
NSScanner* scanner = [NSScanner scannerWithString:*partialStringPtr];
scanner.charactersToBeSkipped = nil;
if(!([scanner scanInt:0] && [scanner isAtEnd])) {
*partialStringPtr = origString;
*proposedSelRangePtr = origSelRange;
NSBeep();
return NO;
}
return YES;
}