Parsing JSON file

Christian Ehrlicher

I just set a break point

When you don't show us your code - how should we help?
Please show us how you try to parse the array, not some debugger output

jenya7

@Christian-Ehrlicher said in Parsing JSON file:

@jenya7 said in Parsing JSON file:

I just set a break point

When you don't show us your code - how should we help?
Please show us how you try to parse the array, not some debugger output

That's all my code

QJsonDocument jsonResponse = QJsonDocument::fromJson(strReply.toUtf8());
QJsonObject jsonObject = jsonResponse.object();
   
QJsonArray daily = jsonObject["[DailyForecasts"].toArray();

in jsonObject I see all objects. daily <0 items>.

KroMignon

@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"

JonB

@jenya7 said in Parsing JSON file:

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

That's why it's so important you show your actual code....

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.