Tree Model Completer Example¶
The Tree Model Completer example shows how to provide completion facilities for a hierarchical model, using a period as the separator to access Child, GrandChild and GrandGrandChild level objects.
Similar to the Completer Example , we provide
QComboBox
objects to enable selection for completion mode and case sensitivity, as well as aQCheckBox
for wrap completions.
The Resource File¶
The contents of the TreeModelCompleter is read from treemodel.txt . This file is embedded within the treemodelcompleter.qrc resource file, which contains the following:
<Code snippet "/data/snapshot-qt5full-5.15/qt5/qtbase/tools/treemodelcompleter/treemodelcompleter.qrc" not found>
TreeModelCompleter Class Definition¶
The
TreeModelCompleter
is a subclass ofQCompleter
with two constructors - one withparent
as an argument and another withparent
andmodel
as arguments.class TreeModelCompleter : public QCompleter { Q_OBJECT Q_PROPERTY(QString separator READ separator WRITE setSeparator) public: explicit TreeModelCompleter(QObject *parent = nullptr); explicit TreeModelCompleter(QAbstractItemModel *model, QObject *parent = nullptr); QString separator() const; public slots: void setSeparator(const QString &separator); protected: QStringList splitPath(const QString &path) const override; QString pathFromIndex(const QModelIndex &index) const override; private: QString sep; };The class reimplements the protected functions
splitPath()
andpathFromIndex()
to suit a tree model. For more information on customizingQCompleter
to suit tree models, refer toHandling Tree Models
.
TreeModelCompleter
also has a separator property which is declared using theQ_PROPERTY()
macro. The separator has READ and WRITE attributes and the corresponding functionsseparator()
andsetSeparator()
. For more information onQ_PROPERTY()
, refer to Qt’s Property System .
TreeModelCompleter Class Implementation¶
The first constructor constructs a
TreeModelCompleter
object with a parent while the second constructor constructs an object with a parent and aQAbstractItemModel
,model
.TreeModelCompleter::TreeModelCompleter(QObject *parent) : QCompleter(parent) { } TreeModelCompleter::TreeModelCompleter(QAbstractItemModel *model, QObject *parent) : QCompleter(model, parent) { }The
separator()
function is a getter function that returns the separator string.QString TreeModelCompleter::separator() const { return sep; }As mentioned earlier, the
splitPath()
function is reimplemented because the default implementation is more suited toQFileSystemModel
or list models. In order forQCompleter
to split the path into a list of strings that are matched at each level, we split it usingsplit()
withsep
as its separator.QStringList TreeModelCompleter::splitPath(const QString &path) const { return (sep.isNull() ? QCompleter::splitPath(path) : path.split(sep)); }The
pathFromIndex()
function returns data for the completionRole() for a tree model. This function is reimplemented as its default implementation is more suitable for list models. If there is no separator, we useQCompleter
‘s default implementation, otherwise we use theprepend()
function to navigate upwards and accumulate the data. The function then returns aQStringList
,dataList
, using a separator to join objects of different levels.QString TreeModelCompleter::pathFromIndex(const QModelIndex &index) const { if (sep.isNull()) return QCompleter::pathFromIndex(index); // navigate up and accumulate data QStringList dataList; for (QModelIndex i = index; i.isValid(); i = i.parent()) dataList.prepend(model()->data(i, completionRole()).toString()); return dataList.join(sep); }
MainWindow Class Definition¶
The
MainWindow
class is a subclass ofQMainWindow
and implements five custom slots:about()
,changeCase()
,changeMode()
,highlight()
, andupdateContentsLabel()
.class MainWindow : public QMainWindow { Q_OBJECT public: MainWindow(QWidget *parent = nullptr); private slots: void about(); void changeCase(int); void changeMode(int); void highlight(const QModelIndex &index); void updateContentsLabel(const QString &sep);In addition, the class has two private functions,
createMenu()
andmodelFromFile()
, as well as private instances ofQTreeView
,QComboBox
,QLabel
,TreeModelCompleter
andQLineEdit
.private: void createMenu(); QAbstractItemModel *modelFromFile(const QString &fileName); QTreeView *treeView = nullptr; QComboBox *caseCombo = nullptr; QComboBox *modeCombo = nullptr; QLabel *contentsLabel = nullptr; TreeModelCompleter *completer = nullptr; QLineEdit *lineEdit = nullptr; };
MainWindow Class Implementation¶
The
MainWindow
‘s constructor creates aMainWindow
object with a parent and initializes thecompleter
andlineEdit
. ThecreateMenu()
function is invoked to set up the “File” menu and “Help” menu. Thecompleter
‘s model is set to theQAbstractItemModel
obtained frommodelFromFile()
, and thehighlighted()
signal is connected toMainWindow
‘shighlight()
slot.MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) { createMenu(); completer = new TreeModelCompleter(this); completer->setModel(modelFromFile(":/resources/treemodel.txt")); completer->setSeparator(QLatin1String(".")); QObject::connect(completer, QOverload<const QModelIndex &>::of(&TreeModelCompleter::highlighted), this, &MainWindow::highlight); QWidget *centralWidget = new QWidget; QLabel *modelLabel = new QLabel; modelLabel->setText(tr("Tree Model<br>(Double click items to edit)")); QLabel *modeLabel = new QLabel; modeLabel->setText(tr("Completion Mode")); modeCombo = new QComboBox; modeCombo->addItem(tr("Inline")); modeCombo->addItem(tr("Filtered Popup")); modeCombo->addItem(tr("Unfiltered Popup")); modeCombo->setCurrentIndex(1); QLabel *caseLabel = new QLabel; caseLabel->setText(tr("Case Sensitivity")); caseCombo = new QComboBox; caseCombo->addItem(tr("Case Insensitive")); caseCombo->addItem(tr("Case Sensitive")); caseCombo->setCurrentIndex(0);The
QLabel
objectsmodelLabel
,modeLabel
andcaseLabel
are instantiated. Also, theQComboBox
objects,modeCombo
andcaseCombo
, are instantiated and populated. By default, thecompleter
‘s mode is “Filtered Popup” and the case is insensitive.QLabel *separatorLabel = new QLabel; separatorLabel->setText(tr("Tree Separator")); QLineEdit *separatorLineEdit = new QLineEdit; separatorLineEdit->setText(completer->separator()); connect(separatorLineEdit, &QLineEdit::textChanged, completer, &TreeModelCompleter::setSeparator); QCheckBox *wrapCheckBox = new QCheckBox; wrapCheckBox->setText(tr("Wrap around completions")); wrapCheckBox->setChecked(completer->wrapAround()); connect(wrapCheckBox, &QAbstractButton::clicked, completer, &QCompleter::setWrapAround); contentsLabel = new QLabel; contentsLabel->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed); connect(separatorLineEdit, &QLineEdit::textChanged, this, &MainWindow::updateContentsLabel); treeView = new QTreeView; treeView->setModel(completer->model()); treeView->header()->hide(); treeView->expandAll(); connect(modeCombo, QOverload<int>::of(&QComboBox::activated), this, &MainWindow::changeMode); connect(caseCombo, QOverload<int>::of(&QComboBox::activated), this, &MainWindow::changeMode); lineEdit = new QLineEdit; lineEdit->setCompleter(completer);We use a
QGridLayout
to place all the objects in theMainWindow
.QGridLayout *layout = new QGridLayout; layout->addWidget(modelLabel, 0, 0); layout->addWidget(treeView, 0, 1); layout->addWidget(modeLabel, 1, 0); layout->addWidget(modeCombo, 1, 1); layout->addWidget(caseLabel, 2, 0); layout->addWidget(caseCombo, 2, 1); layout->addWidget(separatorLabel, 3, 0); layout->addWidget(separatorLineEdit, 3, 1); layout->addWidget(wrapCheckBox, 4, 0); layout->addWidget(contentsLabel, 5, 0, 1, 2); layout->addWidget(lineEdit, 6, 0, 1, 2); centralWidget->setLayout(layout); setCentralWidget(centralWidget); changeCase(caseCombo->currentIndex()); changeMode(modeCombo->currentIndex()); setWindowTitle(tr("Tree Model Completer")); lineEdit->setFocus(); }The
createMenu()
function sets up theQAction
objects required and adds them to the “File” menu and “Help” menu. Thetriggered()
signals from these actions are connected to their respective slots.void MainWindow::createMenu() { QAction *exitAction = new QAction(tr("Exit"), this); QAction *aboutAct = new QAction(tr("About"), this); QAction *aboutQtAct = new QAction(tr("About Qt"), this); connect(exitAction, &QAction::triggered, qApp, &QApplication::quit); connect(aboutAct, &QAction::triggered, this, &MainWindow::about); connect(aboutQtAct, &QAction::triggered, qApp, &QApplication::aboutQt); QMenu *fileMenu = menuBar()->addMenu(tr("File")); fileMenu->addAction(exitAction); QMenu *helpMenu = menuBar()->addMenu(tr("About")); helpMenu->addAction(aboutAct); helpMenu->addAction(aboutQtAct); }The
changeMode()
function accepts anindex
corresponding to the user’s choice of completion mode and changes thecompleter
‘s mode accordingly.void MainWindow::changeMode(int index) { QCompleter::CompletionMode mode; if (index == 0) mode = QCompleter::InlineCompletion; else if (index == 1) mode = QCompleter::PopupCompletion; else mode = QCompleter::UnfilteredPopupCompletion; completer->setCompletionMode(mode); }The
about()
function provides a brief description on the Tree Model Completer example.void MainWindow::about() { QMessageBox::about(this, tr("About"), tr("This example demonstrates how " "to use a QCompleter with a custom tree model.")); }The
changeCase()
function alternates betweenCase Sensitive
andCase Insensitive
modes, depending on the value ofcs
.void MainWindow::changeCase(int cs) { completer->setCaseSensitivity(cs ? Qt::CaseSensitive : Qt::CaseInsensitive); }
main()
Function¶
The
main()
function instantiatesMainWindow
and invokes theshow()
function to display it.int main(int argc, char *argv[]) { Q_INIT_RESOURCE(treemodelcompleter); QApplication app(argc, argv); MainWindow window; window.show(); return app.exec(); }
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