How can I pad an integer on the left with zeros?

Question

I have the following variable:

NSNumber *consumption = [dict objectForKey:@"con"]; 

Which returns 42. How can I pad this number to 10 digits on the left, leading with zeros. The output should look as,

0000000042

or if it were 420,

0000000420

Answer 1

NSString *paddedStr = [NSString stringWithFormat:@"%010d", 42]; 

EDIT: It's C style formatting. %nd means the width is at least n. So if the integer is 2 digit long, then you will have length 3 string (when %3d is used). By default the left empty spaces are filled by space. %0nd (0 between % and n) means 0 is used for padding instead of space. Here n is the total length. If the integer is less than n digits then left padding is used.

Answer 2

The Objective-C way,

NSNumberFormatter * numberFormatter = [[[NSNumberFormatter alloc] init] autorelease]; [numberFormatter setPaddingPosition:NSNumberFormatterPadBeforePrefix]; [numberFormatter setPaddingCharacter:@"0"]; [numberFormatter setMinimumIntegerDigits:10];  NSNumber * number = [NSNumber numberWithInt:42];  NSString * theString = [numberFormatter stringFromNumber:number];  NSLog(@"%@", theString); 

The C way is faster though.