网址参数处理

NSString *codeStr = @"http://qzone.qq.com/?username=aaaa&password=bbbb";
如何截取到"username"?
方法一：根据特殊字符截取：componentsSeparatedByString方法

    NSArray *array1 = [codeStr componentsSeparatedByString:@"?"];
    NSString *str1    = array1[1];//username=aaaa&password=bbbb
    NSArray *array2 = [str1 componentsSeparatedByString:@"&"];
    NSString *str2    = array2[0];//username=aaaa
    NSArray *array3 = [str2 componentsSeparatedByString:@"="];
    NSString *str3    = array3[1];//aaaa
    
    username          = str3;  

方法二：NSURLComponents属性判断：componentsWithString方法
参考资料：http://masilotti.com/nsurlqueryitems/ (免翻译～～)
官方文档：https://developer.apple.com/library/ios/documentation/Foundation/Reference/NSURLComponents_class/index.html#//apple_ref/occ/instp/NSURLComponents/query

    NSURLComponents *urlComponents = [NSURLComponents componentsWithString:inviteCodeStr];
    for (NSURLQueryItem *item in urlComponents.queryItems) {
        if ([item.name isEqualToString:@"username"]) {
            username = item.value;
            return;
        }
    }

其实也就是个key-value。