iphone sdk - Remove all characters except for numbers 0-9 from a string

Question

OK So here's the plan. The XML I'm getting data from allows non-numeric text in phone number fields (for descriptions or contact names, etc). I am trying to extract only the numbers and call the tel: URL with them to initiate a call. Here's whats NOT working:

NSCharacterSet *charset = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
NSString *number = @"(555) 555-5555 Office";
NSString *strippedNumber = [number stringByTrimmingCharactersInSet:charset];
NSString *phoneURL = [NSString stringWithFormat:@"tel:%@", strippedNumber];
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:phoneURL]];

if there are any obvious typos, they're just typos. :)

Answer 1

You're using a trim method, which means that it's only looking at the outer edges of the string. You're probably getting something like: "555) 555-555" as the phone number, correct?

I'm not aware of an NS(Mutable)String method along the lines of "replaceOccurrencesOfCharactersInSet:(NSCharacterSet *)set", and I admit, that'd probably be really nice to have.

Being me, I'd probably just use a regex. If you use RegexKitLite, then you can easily do:

#import "RegexKitLite.h"

NSString * number = @"(555) 555-555 Office";
NSString * strippedNumber = [number stringByReplacingOccurrencesOfRegex:@"[^0-9]" withString:@""];

It might be a bit overkill, but it will do exactly what you're looking for.

FYI: "[^0-9]" means "any character that's not 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9".

Answer 2

your best bet is to get with this: RegexKitLite

and use standard regexs

Answer 3

This seems to be a duplicate of this question:

http://stackoverflow.com/questions/1129521/remove-all-but-numbers-from-nsstring

The answer over there, IMHO, is better than using RegEx.

Answer 4

Although this has already been answered/accepted, I have a better solution without needing an external SDK. Create an additional NSString method in a category like this:

@interface NSString (Helpers)

- (NSString*)stringByRemovingCharactersInSet:(NSCharacterSet*)set;

@end

@implementation NSString (Helpers)

- (NSString*)stringByRemovingCharactersInSet:(NSCharacterSet*)set
{
    NSArray* components = [self componentsSeparatedByCharactersInSet:set];
    return [components componentsJoinedByString:@""];
}

@end

Now you can use stringByRemovingCharactersInSet instead of stringByTrimmingCharactersInSet. However I'd also recommend another slight change to your example code, to support the '+' character in international numbers, as follows:

NSString* number = @"(555) 555-555 Office";
NSCharacterSet* phoneChars = [NSCharacterSet characterSetWithCharactersInString:@"+0123456789"];
NSString* strippedNumber = [number stringByRemovingCharactersInSet:[phoneChars invertedSet]];
NSString* urlString = [NSString stringWithFormat:@"tel:%@", strippedNumber];
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:urlString]];