NSNumberFormatter error from the Apple Documentation "Data Formatting Guide"

I follow the "Data Formatting Guide" from the Apple Developer website:

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
[numberFormatter setFormat:@"0.00%;0.00%;-0.00%"];
NSNumber *four = [NSNumber numberWithFloat:4.0];
NSLog(@"%@", [numberFormatter stringFromNumber:four]);

But it throws an exception:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNumberFormatter setFormat:]: unrecognized selector sent to instance 0x59359b0'

The document was last updated on 2009, so I would not blame on that. My questions are: How do you deal with this error?

Edited Question

How开发者_如何学JAVA do you specify a format on NSNumber? How do you parse a string to a number, a number to string? How do you specify the patterns that Apple pointed to us in a document. I'm talking about iPhone programming. Thank you all!

Edited again

Let's generalize my question: If you take a look at the patterns, let's say I have a string "1 234,57 €" (the last one in the link) and I want to parse this string to a number, I need to specify the format as: "# ##0.00 ¤", but now for iPhone applications, as two people suggested, there's no setFormat: method.

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
[numberFormatter setFormat:@"# ##0.00 ¤"];
NSNumber *dollars = [numberFormatter numberFromString:@"1 234,57 €"];

How do you cope with this?

The link you are looking at is for Mac, not iOS NSNumberFormatterReference

try this:

[numberFormatter setNumberStyle:NSNumberFormatterPercentStyle];

Doesn't look like there is a setFormat: method on a NSNumberFormatter class (even though it's all over the documentation!)

Try the setPositiveFormat: method instead?

Though looking at your example problem, this might be better :

NSLog(@"%f", 4.0f);

or, if you want to store it in a string :

NSString *myString = [NSString stringWithFormat:@"%f", 4.0f]; // You might need to retain this!

Take a look at the string formatting guide.