在http URL等中，不能直接传送等号，会进行有urlencode。

+(NSString*)encodeString:(NSString*)unencodedString{

    // CharactersToBeEscaped = @":/?&=;+!@#$()~',*";

    // CharactersToLeaveUnescaped = @"[].";

    NSString *encodedString = (NSString *)

    CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,

                                                              (CFStringRef)unencodedString,

                                                              NULL,

                                                              (CFStringRef)@"!*'();:@&=+$,/?%#[]",

                                                              kCFStringEncodingUTF8));

    return encodedString;

}

//URLDEcode

-(NSString *)decodeString:(NSString*)encodedString

{

    //NSString *decodedString = [encodedString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding ];

    NSString *decodedString  = (__bridge_transfer NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(NULL,

                                                                                                                     (__bridge CFStringRef)encodedString,

                                                                                                                     CFSTR(""),

}