试试这种方式: -
NSString* sURL = @"www.vanityURL.myWebsitesURL.com";
NSRange lastDotRange = [sURL rangeOfString:@"." options:NSBackwardsSearch];
if (lastDotRange.location != NSNotFound) {
    return [sURL substringToIndex:lastDotRange.location];
} else {
    return sURL;
}