使用MPL从PayPal中的paykey获取交易ID

Question

- (void)paymentSuccessWithKey:(NSString *)payKey andStatus:(PayPalPaymentStatus)paymentStatus {
    status = PAYMENTSTATUS_SUCCESS;

    NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"https://svcs.paypal.com/AdaptivePayments/PaymentDetails"]];

    NSMutableURLRequest *theRequest=[NSMutableURLRequest requestWithURL:url];


    NSString *parameterString = [NSString stringWithFormat:@"payKey=%@&requestEnvelope.errorLanguage=%@",payKey,@"en_US"];

    NSString *msgLength = [NSString stringWithFormat:@"%d", [parameterString length]];

    [theRequest addValue: msgLength forHTTPHeaderField:@"Content-Length"];

    //do post request for parameter passing 
    [theRequest setHTTPMethod:@"POST"];

    [theRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];

    //passing key as a http header request 
    [theRequest addValue:api_username forHTTPHeaderField:@"X-PAYPAL-SECURITY-USERID"];

    //passing key as a http header request
    [theRequest addValue:api_password forHTTPHeaderField:@"X-PAYPAL-SECURITY-PASSWORD"];

    [theRequest addValue:api_signature forHTTPHeaderField:@"X-PAYPAL-SECURITY-SIGNATURE"];

    [theRequest addValue:@"NV" forHTTPHeaderField:@"X-PAYPAL-REQUEST-DATA-FORMAT"];

    [theRequest addValue:@"NV" forHTTPHeaderField:@"X-PAYPAL-RESPONSE-DATA-FORMAT"];

    [theRequest addValue:app_id forHTTPHeaderField:@"X-PAYPAL-APPLICATION-ID"];

    [theRequest setHTTPBody: [parameterString dataUsingEncoding:NSUTF8StringEncoding]];

    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

    if( connection )
    {
        webData = [[NSMutableData data] retain];
    }
    else
    {
        NSLog(@"theConnection is NULL");
    }
}

我以名值格式获得成功回复。如何将其转换为NSDictionary？