JSON help

[Scottish_Jason]

Hi guys... I have been trying for some time to get particular "fields" from this google maps API JSON request. I have successfully been able to get one of the parent results ( formatted_address ) but I would rather be able to get the "long_name" child of address_components. Could somebody give me a little hand with this please?

google maps API JSON

   "results" : [
      {
         "address_components" : [
            {
               "long_name" : "DH5 9QW",
               "short_name" : "DH5 9QW",
               "types" : [ "postal_code" ]
            },
            {
               "long_name" : "School Road",
               "short_name" : "School Rd",
               "types" : [ "route" ]
            },
            {
               "long_name" : "East Rainton",
               "short_name" : "East Rainton",
               "types" : [ "locality", "political" ]
            },
            {
               "long_name" : "Houghton le Spring",
               "short_name" : "Houghton le Spring",
               "types" : [ "postal_town" ]
            },
            {
               "long_name" : "Tyne and Wear",
               "short_name" : "Tyne and Wear",
               "types" : [ "administrative_area_level_2", "political" ]
            },
            {
               "long_name" : "England",
               "short_name" : "England",
               "types" : [ "administrative_area_level_1", "political" ]
            },
            {
               "long_name" : "United Kingdom",
               "short_name" : "GB",
               "types" : [ "country", "political" ]
            }
         ],
         "formatted_address" : "School Rd, East Rainton, Houghton le Spring DH5 9QW, UK",
         "geometry" : {
            "bounds" : {
               "northeast" : {
                  "lat" : 54.8226881,
                  "lng" : -1.4832795
               },
               "southwest" : {
                  "lat" : 54.8216359,
                  "lng" : -1.4868377
               }
            },
            "location" : {
               "lat" : 54.8221041,
               "lng" : -1.4841939
            },
            "location_type" : "APPROXIMATE",
            "viewport" : {
               "northeast" : {
                  "lat" : 54.82351098029149,
                  "lng" : -1.4832795
               },
               "southwest" : {
                  "lat" : 54.8208130197085,
                  "lng" : -1.4868377
               }
            }
         },
         "place_id" : "ChIJew6BECdjfkgR8NnVCEXnCjs",
         "types" : [ "postal_code" ]
      }
   ],
   "status" : "OK"
}

Qt code

void MainWindow::replyFinished(QNetworkReply* reply)
{


   QString strReply = (QString)reply->readAll();

   QJsonDocument jsonResponse = QJsonDocument::fromJson(strReply.toUtf8());

   QJsonObject jsonroot = jsonResponse.object();
   QJsonValue value = jsonroot.value("results");

   QJsonArray array = value.toArray();


QStringList addresses;
QStringList addresses2;

foreach (const QJsonValue & v, array)
{
QJsonObject obj = v.toObject();
QJsonValue val = obj.value("address_components").toString();
qDebug() << "data" <<val << endl;

QJsonObject item = val.toObject();
QJsonValue subobj = item.value("long_name");
QString str = subobj.toString();
qDebug() << "long_name" <<str << endl;



addresses << obj.value("formatted_address").toString();
}

[Paul Colby]

Hi @Scottish_Jason,

There were two problems with the code.

First, this line:

QJsonValue val = obj.value("address_components").toString();

Should not have ended with .toString() ... since address_components is a JSON array, QJsonValue::toString will return a null QString.

Second, this line:

QJsonObject item = val.toObject();

Since item is a JSON array (assuming the first issue above was fixed), QJsonValue::toObject will return an empty QJsonObject.

So a working (though only seeing one long_name) version of your code would be:

QJsonObject obj = v.toObject();
qDebug() << "OBJECT"  << obj;
QJsonValue val = obj.value("address_components"); //< This line changed.
qDebug() << "data" <<val << endl;

QJsonObject item = val.toArray().at(0).toObject(); //< This line changed.
qDebug() << "ITEM" << item;
QJsonValue subobj = item.value("long_name");
QString str = subobj.toString();
qDebug() << "long_name" <<str << endl;

To get all of the long_name values, loop though them too. Here's how I'd do the whole thing:

foreach (const QJsonValue &item, jsonResponse.object().value("results").toArray())
{
    const QJsonObject address = item.toObject();
    foreach (const QJsonValue &component, address.value("address_components").toArray())
    {
        qDebug() << component.toObject().value("long_name");
    }
    qDebug() << address.value("formatted_address");
}

Of course that could do with some error checking too.

Cheers.

[jeremy_k]

It's hard to be certain without a complete function, but there appears to be a level of structure missing in the code.
From the JSON, I see:

object
    array of objects // results
        array of objects // address_components
            string // long_name

The code snippet is missing the second array.

#include <QDebug>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QFile>

int main(int argc, char **argv)
{
    QFile file(argv[1]);
    file.open(QFile::ReadOnly);
    QJsonDocument jsonResponse = QJsonDocument::fromJson(file.readAll());
    QJsonObject jsonroot = jsonResponse.object();
    QJsonValue value = jsonroot.value("results");
    QJsonArray array = value.toArray();
    QStringList addresses;
        
    for (const QJsonValue & v: array) {
        QJsonArray address_components =  v.toObject().value("address_components").toArray();
        for (const QJsonValue & name : address_components) {
            QJsonValue long_name = name.toObject().value("long_name");
            addresses << long_name.toString();
        }
    }
        
    qDebug() << addresses;
    return 0;
}

output: ("DH5 9QW", "School Road", "East Rainton", "Houghton le Spring", "Tyne and Wear", "England", "United Kingdom")

[Scottish_Jason]

Thanks guys. These posts helped me solve my issue.