Json - access data in multidimensional arrays

qDebug

Hello!

I try to access some data from a search result in Json. For example.

[
	{
		"score": 2.899999,
		"site": {
			"id": 1,
			"url": "http://www.google.com",
			"name": "Google.com",
			"type": "search",
			"language": "english",
			"category": [
				"search engine"
			],
			"status": "online",
			"refresh": 30,
			"lastcheck": "2015-12-17",
			"schedule": {
				"time": "20:00",
				"days": [
					"sunday"
				]
			}
		}
	}
]

My code:

QJsonDocument search = QJsonDocument::fromJson(myJson.toUtf8());
QJsonObject getjson = search.object();

QJsonValue arrayValue = getjson.value("site");
QJsonArray jArray = arrayValue.toArray();

qDebug() << jArray.count();

foreach(const QJsonValue & v, jArray)
{
	double vDouble = v.toObject().value("id").toDouble();
	QString my_ID = QString::number(vDouble);
	QString my_NAME = v.toObject().value("name").toString();
	
	qDebug() << "my_ID" << my_ID;
	qDebug() << "my_NAME" << my_NAME;
}

But if the Json looks like this:

{
	"score": 2.899999,
	"site": {
		"id": 1,
		"url": "http://www.google.com",
		"name": "Google.com",
		"type": "search",
		"language": "english",
		"category": [
			"search engine"
		],
		"status": "online",
		"refresh": 30,
		"lastcheck": "2015-12-17",
		"schedule": {
			"time": "20:00",
			"days": [
				"sunday"
			]
		}
	}
}

Without [ and ] at the beginning an end, i can access the data. After a lot of try and error, i can't find the right solution to overcome the [ ]. Anyone knows how?

Thanks!

SGaist

Hi,

Because site is an object and not an array.

QJsonValue siteValue = getjson.value("site");
QJsonObject siteObject = siteValue.toObject();
qDebug() << siteObject.value("id");

qDebug

Yes, but it seems to be an empty object. In jq i would access it like [] .id but

QJsonValue siteValue = getjson.value("site");
QJsonObject siteObject = siteValue.toObject();
qDebug() << siteObject.value("id");

only returns

QJsonValue(undefined)

How can i access data inside an undefined object? I could access it like above if the jsons looks like this

[  "test": { "site": { "id" } } ]

SGaist

@qDebug said:

[ "test": { "site": { "id" } } ]

That's not a valid json structure

qDebug

@SGaist

OK... so, ... well ok, It is not working in Qt. I can access all the data if i command line it through jq (https://stedolan.github.io/jq/) but not in Qt directly.

Your example returns

[
    {
        "score": 2.899999,
        "site": {
            "id": 1,
            "url": "http://www.google.com",
            "name": "Google.com",
            "type": "search",
            "language": "english",
            "category": [
                "search engine"
            ],
            "status": "online",
            "refresh": 30,
            "lastcheck": "2015-12-17",
            "schedule": {
                "time": "20:00",
                "days": [
                    "sunday"
                ]
            }
        }
    }

QJsonValue siteValue = getjson.value("site");
QJsonObject siteObject = siteValue.toObject();
qDebug() << siteObject.value("id");

QJsonValue(undefined)

Why?

Tyras

@qDebug
Maybe because that '[' in JSON's first line should be '{' ?

Tyras

Looking again, it shouldn't even exist...

JKSH

@qDebug said:

Without [ and ] at the beginning an end, i can access the data. After a lot of try and error, i can't find the right solution to overcome the [ ].

[ ] represents an array.
{ } represents an object.

NOTE: Your document does not contain any multidimensional arrays! It does contain objects-inside-arrays, arrays-inside-objects, and objects-inside-objects.

QJsonDocument search = QJsonDocument::fromJson(myJson.toUtf8());
QJsonObject getjson = search.object();

...

QJsonValue(undefined)

Why?

Look closely at your JSON document structure.

Your top-level structure is a JSON array, so you must convert the document to a QJsonArray, not a QJsonObject.

Then, notice that your top-level array contains 1 object. Extract this object from the array first. Then, you can access the object's "site" field (which is also an object).

qDebug

@JKSH

Thank you! That did clear my mind! :D

QJsonDocument to array, then foreach, next object value "site" toObject and now tadaaa object.value("name").toString;

Great, thanks again!