Question

I’m writing a Mac OS X desktop Cocoa app. I’ve got an NSTableView with some values and I’m trying to control those values using a custom NSNumberFormatter.

My desired behavior:

As a user is typing a value, if they type -, I want it to behavior similar to a +/- button on a calculator. So if the user types “500-” then I want to automatically replace that string with “-500”.

Now, I’ve got a working subclass of NSNumberFormatter which handles this situation and returns my desired replacement string. But when I’m typing into my NSTableView, my logs are showing me that “500-” is getting replaced with “-500” but the NSTableView only shows “500” and doesn’t show the – either before OR after.

Is there something I need to do in my xib or in my NSNumberFormatter subclass so that the NSTableView will actually show the negative number?

- (BOOL) isPartialStringValid:(NSString **)partialStringPtr 
       proposedSelectedRange:(NSRangePointer)proposedSelRangePtr 
              originalString:(NSString *)origString 
       originalSelectedRange:(NSRange)origSelRange 
            errorDescription:(NSString **)error

is logging this to the console:

proposed string: 500-
replacement string: -500

But the cell in the NSTableView still shows just “500” afterward.

Answer 1

It turns out that my old school C skills are just rusty and I wasn’t passing the new string back correctly.

I was incorrectly writing:

partialStringPtr = &validString;

But the correct code is:

*partialStringPtr = validString;