objective c - 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.