1.url编码
NSString * newUrlStr = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
stringByAddingPercentEncodingWithAllowedCharacters
api已更换
2.url解码
请求后，返回的数据，如何显示的是这样的格式：%3B%2C%2A，此时需要我们进行UTF-8解码，用到的方法是：
NSString *str = [urlString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
stringByRemovingPercentEncoding