NSNumberFormatter not returning nilSymbol on nil value. What am I missing?

Question

iOS 4+; when I pass a nil value to my NSNumberFormatter I want the nil symbol that was set (NSString *) in return. It works for the 'zero' symbol, but not for the nil symbol. I've tried many different configuration settings like behavior, grouping, etc.

fmtr = [[NSNumberFormatter alloc] init];

[fmtr setNumberStyle:NSNumberFormatterDecimalStyle];

[fmtr setFormatterBehavior:NSNumberFormatterBehaviorDefault];

[fmtr setUsesGroupingSeparator:NO];

[fmtr setNilSymbol:@"###"];

[fmtr setZeroSymbol:@"0000"];

           
NSLog(@"[fmtr nilSymbol]=>>%@<<", [fmtr nilSymbol]);

NSLog(@"[fmtr stringFromNumber:nil]=>>%@<<  this should be '###", [fmtr stringFromNumber:nil] );

NSLog(@"[fmtr stringFromNumber:0]=>>%@<<", [fmtr stringFromNumber:[NSNumber numberWithInt:0]] );

NSLog(@"[fmtr stringFromNumber:null]=>>%@<<", [fmtr stringFromNumber:NULL] );

NSLog(@"[fmtr numberFromString:nil]=%@", [fmtr numberFromString:nil] );

NSLog(@"[fmtr numberFromString:@\"0\"]=%@", [fmtr numberFromString:@"0"] );

NSLog(@"[fmtr numberFromString:NULL]=%@", [fmtr numberFromString:NULL] );

Here is the output of the test:

[fmtr nilSymbol]=>>###<<

[fmtr stringFromNumber:nil]=>>(null)<< this should be '###

[fmtr stringFromNumber:0]=>>0000<<

[fmtr stringFromNumber:null]=>>(null)<<

[fmtr numberFromString:nil]=(null)

[fmtr numberFromString:@"0"]=0

[fmtr numberFromString:NULL]=(null)

Answer 1

I'm not sure exactly why it doesn't work when using numberFromString, but I tested this myself, and it does work if you use "stringForObjectValue" instead. (replace all "stringFromNumber" with "stringForObjectValue")

Edit: Found the answer

On this blog: http://www.nsformatter.com/blog/2010/6/9/nsnumberformatter.html

it says:

• (NSString *)stringFromNumber:(NSNumber *)number;

This is a convenience method. This method returns nil, if number is nil, otherwise it calls -stringForObjectValue:. Therefore it behaves like -stringForObjectValue:, except it never returns the -nilSymbol

It seems to be the purpose of the method (not to use the nilSymbol)