Setting CurrentIndex of comboBox with model

[musti]

I have combobox with model like this

cityModel = new QSqlTableModel(this);
cityModel->setTable("cities"); // (city_id, city_name)
cityModel->select();
comboBox_city->setModel(cityModel);
comboBox_city->setModelColumn(1);
comboBox_city->setCurrentIndex(0);

cityModel = new QSqlTableModel(this);
cityModel->setTable("cities"); // (city_id, city_name)
cityModel->select();
comboBox_city->setModel(cityModel);
comboBox_city->setModelColumn(1);
comboBox_city->setCurrentIndex(0);

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I want to change current index of combobox to row of city_id has 15 value?
Please help me.

Following line doesnt work.

comboBox_city->setCurrentIndex(comboBox_city->findData(query.value(rec.indexOf("city_id"))) );

comboBox_city->setCurrentIndex(comboBox_city->findData(query.value(rec.indexOf("city_id"))) );

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