Parsing JSON file

Christian Ehrlicher

And you still not show us how you try to access the single array elements nor what the debug output suggested by @JonB prints out.

jenya7

@KroMignon said in Parsing JSON file:

@jenya7 said in Parsing JSON file:

QJsonArray daily = jsonObject["[DailyForecasts"].toArray();

I don't known if it is a copy past from your real code.
If it is the case there is a typo ==> "[DailyForecasts" should be "DailyForecasts"

Yes. Sorry. Was my typo. Now it seems to be OK.
But how can I go further?

 QJsonArray daily1 = jsonObject["DailyForecasts"].toArray();
 QJsonArray temp = daily1 [?].?

jenya7

@Christian-Ehrlicher said in Parsing JSON file:

And you still not show us how you try to access the single array elements nor what the debug output suggested by @JonB prints out.

I still don't know how to do it. :)

KroMignon

@jenya7 said in Parsing JSON file:

I still don't know how to do it. :)

Yes, Qt documentation about JSON is a little bit short (https://doc.qt.io/qt-5/json.html).
You can iterate through the array:


for(const auto & dayValue : jsonObject["DailyForecasts"].toArray())
{
    // convert value to object
    QJsonObject day = dayValue.toObject();
    // according to your post, temperature seems to be an object, not an array
    QJsonObject temperature = day["Temperature"].toObject();

}

jenya7

@KroMignon said in Parsing JSON file:

@jenya7 said in Parsing JSON file:

I still don't know how to do it. :)

Yes, Qt documentation about JSON is a little bit short (https://doc.qt.io/qt-5/json.html).
You can iterate through the array:
for(const auto & dayValue : jsonObject["DailyForecasts"].toArray())
{
    // convert value to object
    QJsonObject day = dayValue.toObject();
    // according to your post, temperature seems to be an object, not an array
    QJsonObject temperature = day["Temperature"].toObject();

}

Thank you. It works. And how to get objects inside the "Temperature"?
"Temperature"->"Maximum"->"Value"
"Temperature"->"Minimum"->"Value"
I wonder why I can't access it like this

QJsonArray temp = daily[0].toArray();

I get no errors but it doesn't work.

KroMignon

@jenya7 said in Parsing JSON file:

I get no errors but it doesn't work.

Why should it work?
You are trying to convert QJsonValue to QJsonArray, but according to your post it is a QJsonObject.

You could use QJsonValue::isObject() or QJsonValue::isArray() to ensure value type before converting.
But, as you know the right type, you only have to use the right functions ;)

jenya7

I'm lost from this point on. The best I could find

QJsonValue temp_max = temperature.value("Maximum");

Doesn't work.

J.Hilk

@jenya7
there is not much magic to it:

"key": [] // Array
"key":{} //Object
"key":everything else //value

KroMignon

@jenya7 said in Parsing JSON file:

I'm lost from this point on. The best I could find
   QJsonValue temp_max = temperature.value("Maximum");
Doesn't work.

What do you mean with does not work?

This should work:

for(const auto & dayValue : jsonObject["DailyForecasts"].toArray())
{
    // convert value to object
    QJsonObject day = dayValue.toObject();
    // according to your post, temperature seems to be an object, not an array
    QJsonObject temperature = day["Temperature"].toObject();
    QJsonObject maxTemp = temperature["Maximum"].toObject();
    QJsonObject minTemp = temperature["Minimum"].toObject();
    if(!maxTemp.isEmpty())
        qDebug() << "'MaxTemp is" << maxTemp["Value"].toDouble() << maxTemp["Unit"].toString();
    if(!minTemp.isEmpty())
        qDebug() << "'MinTemp is" << minTemp["Value"].toDouble() << minTemp["Unit"].toString();   
}

JonB

@jenya7
As @KroMignon says.

While you are developing, and not understanding how your JSON is parsed/what objects/arrays etc. it is composed of, make use of QJsonValue::Type QJsonValue::type() const and enum QJsonValue::Type. If you print this all the time you would know how the JSON is being parsed, e.g.

qDebug() << jsonObject["DailyForecasts"].type() << day["Temperature"].type() << temperature["Maximum"].type()

etc. That's how you know whether you can go toObject/toArray/toString() etc.

jenya7

@KroMignon said in Parsing JSON file:

@jenya7 said in Parsing JSON file:

I'm lost from this point on. The best I could find
   QJsonValue temp_max = temperature.value("Maximum");
Doesn't work.

What do you mean with does not work?

This should work:

for(const auto & dayValue : jsonObject["DailyForecasts"].toArray())
{
    // convert value to object
    QJsonObject day = dayValue.toObject();
    // according to your post, temperature seems to be an object, not an array
    QJsonObject temperature = day["Temperature"].toObject();
    QJsonObject maxTemp = temperature["Maximum"].toObject();
    QJsonObject minTemp = temperature["Minimum"].toObject();
    if(!maxTemp.isEmpty())
        qDebug() << "'MaxTemp is" << maxTemp["Value"].toDouble() << maxTemp["Unit"].toString();
    if(!minTemp.isEmpty())
        qDebug() << "'MinTemp is" << minTemp["Value"].toDouble() << minTemp["Unit"].toString();   
}

It works. Thank you.

KroMignon

@jenya7 said in Parsing JSON file:

It works. Thank you.

But you did not reply to my question... What exactly did not work with your code?
AFAIK, there is no difference between temperature.value("Maximum") and temperature["Maximum"].

jenya7

@KroMignon said in Parsing JSON file:

@jenya7 said in Parsing JSON file:

It works. Thank you.

But you did not reply to my question... What exactly did not work with your code?
AFAIK, there is no difference between temperature.value("Maximum") and temperature["Maximum"].

Yes. It should be the same. Probably I didn't cast it to the right data type.