LBUrlUtilities.m

/// 获取 url 的顶级域名. 比如, a.example.com 的顶级域名是 example.com
- (NSString *)topLevelDomainNameFromUrl:(NSURL *)url {
    if (url.absoluteString.length == 0) {
        return nil;
    }
    
    NSString *topLevelDomainName = @"";
    NSString *host = url.host;
    NSArray *subStrings = [host componentsSeparatedByString:@"."];
    NSUInteger count = subStrings.count;
    if (count == 2) {
        topLevelDomainName = host;
    } else if (count > 2) {
        topLevelDomainName = [NSString stringWithFormat:@"%@.%@", subStrings[count - 2], subStrings[count - 1]];
    } else {
        return nil;
    }
    
    return topLevelDomainName;
}