url字符串中具有特殊功能的特殊字符的字符串，或者中文字符,作为参数用GET方式传递时，需要用urlencode处理一下
//URLEncode
+(NSString*)encodeString:(NSString*)unencodedString{
if([[[UIDevicecurrentDevice]systemVersion]floatValue] >=9.0) {
return[unencodedString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLPathAllowedCharacterSet]];
}
NSString*encodedString = (NSString*)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,(CFStringRef)unencodedString,NULL,(CFStringRef)@"!*'();:@&=+$,/?%#[]",kCFStringEncodingUTF8));
returnencodedString;
}//URLDEcode
-(NSString *)decodeString:(NSString*)encodedString
{
//NSString *decodedString = [encodedString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding ];
NSString *decodedString = (__bridge_transfer NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(NULL,
(__bridge CFStringRef)encodedString,
CFSTR(""),
CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding));
return decodedString;
有用户反馈，说iOS9之后，CFURLCreateStringByAddingPercentEscapes这个方法废弃，所以根据官方的描述 替换使用stringByAddingPercentEncodingWithAllowedCharacters 这个方法。
stringByAddingPercentEncodingWithAllowedCharacters 需要传递参数NSCharacterSet 。
