Find the right qt data model with variable fields - c++

Question

I am looking for a datamodel. Qt offers a lot of options, so I would like your advice.
Here is the simpified example of the structure of my datamodel:
It has two fields: field 1 and field 2.
Field1 can be "none", "option" or "number"
If field1 is "none", field2 should be empty and contain no options.
If field1 is "option", field2 should give me an option for "a" or "b"
If field1 is "number", field2 should give me the option to enter any number between 1 and 100.
I would like to have a table like view of this data on a form, with combo or spinboxes to select the data. It should not be possible to enter any other data than specified.
Could you please point me in the right direction and maybe provide an example of how to implement this in the most simple way in Qt.
I want to be able to store this data as well to a file, for which I probably will use json.

Answer 1

Assumed you are aware of Qt's model/view system, and knows that you should use View to visualize your data model, Then what you are going to implement further more is delegate , which could offer extra interface other than text input for each field.
According to this tutorial , you should do these:
Subclassing QStyledItemDelegate , create your own delegate class , e.g MyDelegate
class MyDelegate : public QStyledItemDelegate
{
Q_OBJECT
public:
enum FIELDS
{
COL_FIELD1,
};
explicit MyDelegate(QObject *parent = nullptr);
QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option,
const QModelIndex &index) const Q_DECL_OVERRIDE;
void setEditorData(QWidget *editor, const QModelIndex &index) const Q_DECL_OVERRIDE;
void setModelData(QWidget *editor, QAbstractItemModel *model,
const QModelIndex &index) const Q_DECL_OVERRIDE;
void updateEditorGeometry(QWidget *editor,
const QStyleOptionViewItem &option, const QModelIndex &index) const Q_DECL_OVERRIDE;
};
Implement these functions
createEditor, define what kind of widget offering for user to do editing task
setEditorData, convert data from DataModel to widget
setModelData, convert data from Widget to DataModel
updateEditorGeometry, define widget looking in the field.
On following codes, i tried to figure out your need to offer options of field1.
#include "mydelegate.h"
MyDelegate::MyDelegate(QObject *parent) : QStyledItemDelegate(parent)
{
}
QWidget* MyDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
QComboBox* __comboBox = new QComboBox(parent);
if(index.column()==COL_FIELD1)
{
__comboBox->addItem("none");
__comboBox->addItem("option");
__comboBox->addItem("number");
}
else
{
//! according to your need...
}
return __comboBox;
}
void MyDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
QComboBox* __comboBox = qobject_cast<QComboBox*>(editor);
if(index.column()==COL_FIELD1)
{
__comboBox->setCurrentText(index.model()->data(index).toString());
}
}
void MyDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
QComboBox* __comboBox = qobject_cast<QComboBox*>(editor);
model->setData(index,QVariant::fromValue(__comboBox->currentText()));
}
void MyDelegate::updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
editor->setGeometry(option.rect);
}
instanized MyDelegate , attach to your View
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
//! prepare a demo model
QStringListModel *model = new QStringListModel();
QStringList list;
list << "a" << "b" << "c";
model->setStringList(list);
//! attach a MyDelegate for Row1
ui->tableView->setModel(model);
ui->tableView->setItemDelegateForRow(0,new MyDelegate(this));
}
MainWindow::~MainWindow()
{
delete ui;
}
Demostrated effect would like this:
Just tried changed the contents on the implementation of MyDelegate to get the effects you need (e.g spinBox , or different options for Field2) , have fun!