NSString字符串encode与decode

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

1.URL ENCODE

 + (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;

 }
 

2.URL DECODE

-(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