Extracting a URL from within a string

Question

My app receives numerous text strings which may or may not contain a URL anywhere within the string. What would be the best method to extract a URL from within a string? Thank you.

Answer 1

Regexp is always nice: ^(ht|f)tp:\/\/(w{3}\.)?([\w-]\.*)*([a-zA-Z]{2,4})(\?[\w]+=[\w]+((&[\w]+=[\w]+)*)?)?$/gm

Answer 2

The BSD-licensed AutoHyperlinks framework provides classes to scan text for URLs and either return them to you or mark them up as links in an attributed string.

I don't think it builds out of the box for the iPhone, but you could always add preprocessor directives to cut out any AppKit-dependent code. The scan-and-return interface should just work, once you get it to build. (Make sure to run the tests.)

Mike Abdullah wrote a patch for iPhone support. You might try that.

Answer 3

If you are working on a Mac application, Mac OS X 10.6 offers a new API to let you detect URLs with the spell checker. You may do it this way.

NSString *s = @"http://example.com"
NSInteger wordCount = 0;
NSOrthography *orthography = nil;
NSArray *checkResults = [[NSSpellChecker sharedSpellChecker] checkString:s range:NSMakeRange(0, [s length]) types:NSTextCheckingTypeLink options:nil inSpellDocumentWithTag:0 orthography:&orthography wordCount:&wordCount];
for (NSTextCheckingResult *result in checkResults) {
    NSRange range = result.range;
    NSURL *URL = result.URL;
}