Question

Is there any API or good function to format strings like
“www.example.com” or just “example.com” to valid urlstrings like
“http://www.example.com”?

+ (NSString*)complete:(NSString *)urlString
{
    NSArray * urlParts = [urlString componentsSeparatedByString:@"."];
    if(urlParts.count==3)
        return [NSString stringWithFormat:@"http://www.%@.%@",[urlParts objectAtIndex:1],[urlParts objectAtIndex:2]];
    else if(urlParts.count==2)
        return [NSString stringWithFormat:@"http://www.%@.%@",[urlParts objectAtIndex:0],[urlParts objectAtIndex:1]];
    return nil;
}

this is what current solution looks like, but this doesn’t look very good and solid to me.

Answer 1

You can do this fairly easily with NSDataDetector:

NSDataDetector *detector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:NULL];
NSString *URLString = @"www.example.com";
NSTextCheckingResult *result = [detector firstMatchInString:URLString options:0 range:NSMakeRange(0, URLString.length)];
if (result) {
    NSURL *URL = [result URL];
    NSLog(@"%@", URL); // http://www.example.com
}

You should not assume that www is a valid subdomain for any given domain btw.

If you need the result as a string, you can use the absoluteString method of NSURL, it’s typically better to use NSURL instead of NSString for URLs though.