[Interest] iterate through JSON data

[Hamish Moffatt]

On 17/05/16 12:02, Larry Martell wrote:
> On Mon, May 16, 2016 at 7:53 PM, Hamish Moffatt
> <hamish at risingsoftware.com> wrote:
>> On 17/05/16 08:24, Larry Martell wrote:
>>> I've see a lot of code that does something like this:
>>>
>>>       QJsonDocument document = QJsonDocument::fromJson(jsonData);
>>>       QJsonObject object = document.object();
>>>       QJsonValue value = object.value("capData");
>>>
>>> But I don't want to hard code the keys - I want to pick up and store
>>> whatever happens to be in the JSON file. How can I iterate through it
>>> and do that?
>>>
>>> Also, what would be the best object to store this in so I can later
>>> access it as I want to?
>>>
>> QJsonObject has iterator methods, and for each value you can check if it is
>> itself an array or an object or a simple type (QJsonValue::isArray(),
>> isObject(), isString() etc).
>>
>> As for another object, I can't think of another with this flexibility. Why
>> not leave it in the QJson* objects?
> My JSON file looks like this:
>
>
> {
>     "capData": {
>        "host": "foo.bar.com",
>        "initial_port": "8000"
>        "secondary_port": "8001"
>     },
>     "django": {
>        "host": "baz.bar.com",
>        "port": "8004"
>     }
> }
>
>
> My code looks like this:
>
>
>    QFile file(QCoreApplication::applicationDirPath() + "/" + CONFIG_PATH);
>    QByteArray val;
>    QJsonDocument config_json;
>    QJsonObject config;
>
>    if (file.open(QIODevice::ReadOnly | QIODevice::Text)) {
>      val = file.readAll();
>      file.close();
>      config_json = QJsonDocument::fromJson(val);
>      config = config_json.object();
>      QJsonValue value = config.value("capData");
>      QJsonArray array = value.toArray();
>      foreach (const QJsonValue & v, array)
>          qWarning() << v.toObject().value("host").toString();
>    }
>
> I never enter my foreach loop, so I wrote out each variable with qWarning().
>
> When I print out val it has:
>
> "{\n   \"capData\": {\n      \"host\": \"foo.bar.com\",\n
> \"initial_port\": \"8000\"\n      \"secondary_port\": \"8001\"\n
> },\n   \"django\": {\n      \"host\": \"baz.bar.com\",\n
> \"port\": \"8004\"\n   }\n}\n"
>
> But when I print out config_json I get:
>
> QJsonDocument()

Your JSON is invalid - you're missing a comma on the end of the 
initial_port line. config_json.isEmpty() is true as a result, and 
isObject() is false.


Hamish