NSString doesn't overwrites with a new value - objective-c

Question

Trying to remove all the urls from text:
- (NSString *)cleanText:(NSString *)text{
NSString *string = #"This is a sample of a http://abc.com/efg.php?EFAei687e3EsA sentence with a URL within it.";
NSDataDetector *linkDetector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:nil];
NSArray *matches = [linkDetector matchesInString:string options:0 range:NSMakeRange(0, [string length])];
for (NSTextCheckingResult *match in matches) {
if ([match resultType] == NSTextCheckingTypeLink) {
NSString *matchingString = [match description];
NSLog(#"found URL: %#", matchingString);
string = [string stringByReplacingOccurrencesOfString:matchingString withString:#""];
}
}
NSLog(string);
return string;
}
However string returns unchanged (there is match).
Upd.: Console output:
found URL: <NSLinkCheckingResult: 0xb2b03f0>{22, 36}{http://abc.com/efg.php?EFAei687e3EsA}
2013-10-02 20:19:52.772
This is a sample of a http://abc.com/efg.php?EFAei687e3EsA sentence with a URL within it and a number 097843.
Ready working recipe done by #Raphael Schweikert.

Answer 1

The problem is that [match description] does not return the matching string; it returns a string that looks like this:
"<NSLinkCheckingResult: 0x8cd5150>{22,36}{http://abc.com/efg.php?EFAei687e3EsA}"
To replace the matched URL in your string, you should do:
string = [string stringByReplacingCharactersInRange:match.range withString:#""];

Answer 2

According to Apple’s own Douglas Davidson, the matches are guaranteed to be in the order they appear in the string. So instead of sorting the matches array (as I suggested), it can just be iterated in reverse.
The whole code sample would then look as follows:
NSString *string = #"This is a sample of a http://abc.com/efg.php sentence (http://abc.com/efg.php) with a URL within it and some more text afterwards so there is no index error.";
NSDataDetector *linkDetector = [NSDataDetector dataDetectorWithTypes:0|NSTextCheckingTypeLink error:nil];
NSArray *matches = [linkDetector matchesInString:string options:0 range:NSMakeRange(0, [string length])];
for (NSTextCheckingResult *match in [matches reverseObjectEnumerator]) {
string = [string stringByReplacingCharactersInRange:match.range withString:#""];
}
The check for match.resultType == NSTextCheckingTypeLink can be omitted as you’ve already specified in the options that you’re only interested in links.