NSString转化为NSDictionary

NSString *jsonStr = @"{
  "api": "ccf.cart2.queryPointsBalance",
  "code": "1",
  "v": "1.0",
  "msg": "",
  "data": {
    "totalBalanceQuantity": "4",
    "totalBalanceAmt": "0.04",
    "errorInfos": {
      "errorCode": "",
      "errorMessage": ""
    }
  }
}";

NSString *jsonStr = @"{\"api\":\"ccf.cart2.queryPointsBalance\",\"code\":\"1\",\"v\":\"1.0\",\"msg\":\"\",\"data\":{\"totalBalanceQuantity\":\"4\",\"totalBalanceAmt\":\"0.04\",\"errorInfos\":{\"errorCode\":\"\",\"errorMessage\":\"\"}}}";
NSData *data = [jsonStr dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *tempDictQueryDiamond = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];

{
    api = "ccf.cart2.queryPointsBalance";
    code = 1;
    data =     {
        errorInfos =         {
            errorCode = "";
            errorMessage = "";
        };
        totalBalanceAmt = "0.04";
        totalBalanceQuantity = 4;
    };
    msg = "";
    v = "1.0";
}