How to dynamically create varying number of widgets based on user input

[lukutis222]

Hello. In my program, I would like to create different number of radiobuttons.

At the moment, I manually create 3 radio buttons using:

in my header I declare the widgets:

    QScrollArea *scrollArea;
    QWidget *scrollAreaWidgetContents;
    QPushButton *start_test_button;
    QRadioButton *radioButton;
    QRadioButton *radioButton_2;
    QRadioButton *radioButton_3;
    QRadioButton *radioButton_4;

in my cpp:

void TestTool::Create_widgets(QMainWindow *parent){

    scrollArea = new QScrollArea(parent);
    scrollArea->setObjectName(QString::fromUtf8("scrollArea"));
    scrollArea->setGeometry(QRect(30, 110, 481, 371));
    scrollArea->setWidgetResizable(true);
    scrollAreaWidgetContents = new QWidget();
    scrollAreaWidgetContents->setObjectName(QString::fromUtf8("scrollAreaWidgetContents"));
    scrollAreaWidgetContents->setGeometry(QRect(0, 0, 479, 369));
    radioButton = new QRadioButton(scrollAreaWidgetContents);
    radioButton->setObjectName(QString::fromUtf8("radioButton"));
    radioButton->setGeometry(QRect(50, 50, 150, 20));
    radioButton_2 = new QRadioButton(scrollAreaWidgetContents);
    radioButton_2->setObjectName(QString::fromUtf8("radioButton_2"));
    radioButton_2->setGeometry(QRect(50, 100, 150, 20));
    radioButton_3 = new QRadioButton(scrollAreaWidgetContents);
    radioButton_3->setObjectName(QString::fromUtf8("radioButton_3"));
    radioButton_3->setGeometry(QRect(50, 150, 150, 20));

    scrollArea->setWidget(scrollAreaWidgetContents);

    start_test_button = new QPushButton(scrollAreaWidgetContents);
    start_test_button->setObjectName(QString::fromUtf8("start_test_button"));
    start_test_button->setGeometry(QRect(50, 20, 150, 24));
    start_test_button->setText(QCoreApplication::translate("Widget", "Start test", nullptr));

    radioButton->setText(QCoreApplication::translate("Widget", "test1", nullptr));
    radioButton_2->setText(QCoreApplication::translate("Widget", "test2", nullptr));
    radioButton_3->setText(QCoreApplication::translate("Widget", "test3", nullptr));

    scrollArea->show();
}

and it works fine:

However, instead of manually creating specific amount of radiobutton widgets, I need to be able to create large amount of radiobuttons (up to 100) based on user choice. In my program, user can select a specific testing scenario that he wants to perform and based on this selection I will determine how many unique tests will need to be performed and for each unique test I need to create radiobutton.

So lets say I have a list of structure:

struct dynamic_widget_s{
   Qstring widget_button_name;
   uint8_t widget_number;
};

QList<dynamic_widget_s> widget_struct;

Imagine I have a list of 10 structures:

widget_struct[0].button_name = "button1";
widget_struct[0].widget_number = 1;

widget_struct[1].button_name = "button2";
widget_struct[1].widget_number = 2;

widget_struct[2].button_name = "button3";
widget_struct[2].widget_number = 3;

widget_struct[3].button_name = "button4";
widget_struct[3].widget_number = 4;

widget_struct[4].button_name = "button5";
widget_struct[4].widget_number = 5;

widget_struct[5].button_name = "button6";
widget_struct[5].widget_number = 6;

widget_struct[6].button_name = "button7";
widget_struct[6].widget_number = 7;

widget_struct[7].button_name = "button8";
widget_struct[7].widget_number = 8;

widget_struct[8].button_name = "button9";
widget_struct[8].widget_number = 9;

widget_struct[9].button_name = "button10";
widget_struct[9].widget_number = 10;

and I want to create 10 unique radiobuttons and display them on my application. Could someone point me in the right direction and suggest me a best way to do this?

Keep in mind that the structure is assigned only during runtime of the application so the number of widgets that I will need to create may vary.

[jsulm]

@lukutis222 said in How to dynamically create varying number of widgets based on user input:

Could someone point me in the right direction and suggest me a best way to do this?

What exactly is the problem?
You create a new button like this:

QPushButton *newButton = new QPushButton(QIcon(), widget_struct[i].button_name, this);
// Now add it to a layout where you want to have it

[lukutis222]

@jsulm
Thanks for the response.
I still do not understand how can I dynamically create this.
Lets say I want to create 10 radiobuttons:

    for(int i=0; i < 10; i ++){
        QRadioButton *radiobutton = new QRadioButton(widget_struct[i].button_name, this);
    }

The code above will not work becuase the QRadioButton object (radiobutton) will be overwritten 10 times.
How can I ensure that I have unique object for each button?

I cant simply do:

        QRadioButton *radiobutton1 = new QRadioButton(widget_struct[0].button_name, this);

        QRadioButton *radiobutton2 = new QRadioButton(widget_struct[1].button_name, this);

        QRadioButton *radiobutton3 = new QRadioButton(widget_struct[2].button_name, this);

        QRadioButton *radiobutton4 = new QRadioButton(widget_struct[3].button_name, this);

        QRadioButton *radiobutton5 = new QRadioButton(widget_struct[4].button_name, this);

        QRadioButton *radiobutton6 = new QRadioButton(widget_struct[5].button_name, this);

        QRadioButton *radiobutton7 = new QRadioButton(widget_struct[6].button_name, this);

        QRadioButton *radiobutton8 = new QRadioButton(widget_struct[7].button_name, this);

        QRadioButton *radiobutton9 = new QRadioButton(widget_struct[8].button_name, this);

       QRadioButton *radiobutton10 = new QRadioButton(widget_struct[9].button_name, this);

Unless I know how many buttons I am going to have before runtime. Unfortunately I do not because that will depend on user choise.

What you suggested is simply manually creating button. What if I need to create 100 of them?

[Chris Kawa]

@lukutis222 If you don't need to hold on to them then just create the button in a loop and use it immediately e.g.

for(int i=0; i < 10; i ++){
   QRadioButton *radiobutton = new QRadioButton(widget_struct[i].button_name, this);

   // for example:
   someWidget->layout()->addWidget(radiobutton);
   connect(radiobutton, &QRadioButton::toggled, something, &SomeClass::someSlot);
}

If you need to hold on to the pointer for something just put them in a container:

QVector<QRadioButton*> buttons;

for(int i=0; i < 10; i ++){
   QRadioButton *radiobutton = new QRadioButton(widget_struct[i].button_name, this);
   buttons << radiobutton.
}

and you can then use them as buttons[42] or iterate over the vector or do whatever you want with them.

[mpergand]

I suggest to add a variable to the struct:

struct dynamic_widget_s{
   Qstring widget_button_name;
   uint8_t widget_number;
QRadioButton* button;
};

for(int i=0; i < 10; i ++){
        struct[i].button = new QRadioButton(widget_struct[i].button_name, this);
    }

[lukutis222]

@Chris-Kawa @mpergand
Both great solutions. I do not know why I didint think about that.. Thank you very much!