Question

Possible Duplicate:
Removing leading zeroes from a string

I need to remove 0 from the beginning of a string and prevent leading 0s when user input the number, how can I do it?

For example:
user input: 000090
display: 90

Thanks!

Answer 1

One approach is to use an NSScanner:

NSString *string = @"000090";
NSCharacterSet *nonzeroNumberCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@"123456789"];
NSScanner *scanner = [NSScanner scannerWithString:string];
[scanner scanUpToCharactersFromSet:nonzeroNumberCharacterSet intoString:nil];
NSString *remainder = nil;
NSCharacterSet *emptyCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@""];
[scanner scanUpToCharactersFromSet:emptyCharacterSet intoString:&remainder];

At this point remainder is equal to @"90".

Equivalently, one could replace the lines

NSCharacterSet *nonzeroNumberCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@"123456789"];
NSScanner *scanner = [NSScanner scannerWithString:string];

with

NSCharacterSet *zeroNumberCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@"0"];
[scanner scanCharactersFromSet:zeroNumberCharacterSet intoString:nil];

to scan past all the zeros rather than to scan until the first non-zero number.

One drawback of this approach is that if the original string is @"000000000", the resulting string will be empty.