NSNumberFormatter Error from Apple Documentation "Data Formatting Guide"

Question

I follow the " Data Formatting Guide " on 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 in 2009, so I would not blame it. My questions are: how do you deal with this error?

Edited Question

How do you define the format for NSNumber? How do you parse a string into a number, a number into a string? How do you define the patterns that Apple indicated to us in the document . I am talking about programming iPhone. Thanks everyone!

Edited again

: , , "1 234,57 €" ( ), , "# ## 0.00 ¤", iPhone, , setFormat:,

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

?

Answer 1

, , Mac, iOS NSNumberFormatterReference

:

[numberFormatter setNumberStyle:NSNumberFormatterPercentStyle];

Answer 2

, setFormat: NSNumberFormatter ( !)

setPositiveFormat:?

---

, :

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

, :

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

.