JSON IPHONE: How to send a JSON request and pull data from the server?

Question

I don’t know anything about JSON, and I need to send a request to the server and read the data coming from it using only the iPhone.

I tried using the jason-framework for this, but after reading the documents, I was not able to figure out how to build the object and send it on request. So I decided to adapt another code that I saw here on SO.

The object I need is:

{"code": xxx}

I have a problem here. This xxx is NSData, so I suspect that I need to convert this data to a string, and then use this string to create an object and send it on request.

server response is also a JSON object in the form

{"answer": "yyy"} where yyy is a number between 10,000 and 99999

this is the code that i still have.

- (NSString *)checkData:(NSData) theData {
    NSString *jsonObjectString = [self encode:(uint8_t *)theData length:theData.length];      
    NSString *completeString = [NSString stringWithFormat:@"http://www.server.com/check?myData=%@", jsonObjectString];                               
    NSURL *urlForValidation = [NSURL URLWithString:completeString];               
    NSMutableURLRequest *validationRequest = [[NSMutableURLRequest alloc] initWithURL:urlForValidation];                          
    [validationRequest setHTTPMethod:@"POST"];             
    NSData *responseData = [NSURLConnection sendSynchronousRequest:validationRequest returningResponse:nil error:nil];  
    [validationRequest release];
    NSString *responseString = [[NSString alloc] initWithData:responseData encoding: NSUTF8StringEncoding];
    NSInteger response = [responseString integerValue];
    NSLog(@"%@", responseString);
    [responseString release];
    return responseString;
}


- (NSString *)encode:(const uint8_t *)input length:(NSInteger)length {
    static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    NSMutableData *data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
    uint8_t *output = (uint8_t *)data.mutableBytes;

    for (NSInteger i = 0; i < length; i += 3) {
        NSInteger value = 0;
        for (NSInteger j = i; j < (i + 3); j++) {
            value <<= 8;

            if (j < length) {
                value |= (0xFF & input[j]);
            }
        }

        NSInteger index = (i / 3) * 4;
        output[index + 0] = table[(value >> 18) & 0x3F];
        output[index + 1] =                    table[(value >> 12) & 0x3F];
        output[index + 2] = (i + 1) < length ? table[(value >> 6)  & 0x3F] : '=';
        output[index + 3] = (i + 2) < length ? table[(value >> 0)  & 0x3F] : '=';
    }

    ret

    urn [[[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding] autorelease];
}

all this code gives me errors. Either a BAD URL or java exception.

What is wrong with this code?

If you guys want to give another solution using json-framework, tell me how to encode an object using this pair ("code", "my NSData are converted to a string here") ...

Thanks for any help.

Answer 1

JSON , , , . , , . NSData :

NSString* stringData = [[NSString alloc] initWithData:yourData
                                             encoding:NSUTF8StringEncoding];

, ( ), , Base64 ( http://www.cocoadev.com/index.pl?BaseSixtyFour ). NSData Base64.

code stringData ( ):

NSDictionary* jsonDictionary = [NSDictionary dictionaryWithObject:stringData
                                                           forKey:@"code"];

JSON. JSON.h , :

NSString* jsonString = [jsonDictionary JSONRepresentation];

, JSON - - : { "code" : "{yourstringdata}"; }. - ASIHTTPRequest POST.

, JSON , :

NSDictionary* responseDict = [yourJSONResponseStringFromServer JSONValue];
NSNumber* answerNum = (NSNumber *) [responseDict objectForKey:@"answer"];
int answer = [answerNum intValue];