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This is achieved by using multiple views on the same model, each of which is filtered using an instance of the QSortFilterProxyModel class. \section1 Overview The address book contains 5 classes: \c MainWindow, \c AddressWidget, \c TableModel, \c NewAddressTab and \c AddDialog. The \c MainWindow class uses \c AddressWidget as its central widget and provides \gui File and \gui Tools menus. \image addressbook-classes.png Diagram for Address Book Example The \c AddressWidget class is a QTabWidget subclass that is used to manipulate the 10 tabs displayed in the example: the 9 alphabet group tabs and an instance of \c NewAddressTab. The \c NewAddressTab class is a subclass of QWidget that is only used whenever the address book is empty, prompting the user to add some contacts. \c AddressWidget also interacts with an instance of \c TableModel to add, edit and remove entries to the address book. \c TableModel is a subclass of QAbstractTableModel that provides the standard model/view API to access data. It also holds a QList of \l{QPair}s corresponding to the contacts added. However, this data is not all visible in a single tab. Instead, QTableView is used to provide 9 different views of the same data, according to the alphabet groups. QSortFilterProxyModel is the class responsible for filtering the contacts for each group of contacts. Each proxy model uses a QRegExp to filter out contacts that do not belong in the corresponding alphabetical group. The \c AddDialog class is used to obtain information from the user for the address book. This QDialog subclass is instantiated by \c NewAddressTab to add contacts, and by \c AddressWidget to add and edit contacts. We begin by looking at the \c TableModel implementation. \section1 TableModel Class Definition The \c TableModel class provides standard API to access data in its QList of \l{QPair}s by subclassing QAbstractTableModel. The basic functions that must be implemented in order to do so are: \c rowCount(), \c columnCount(), \c data(), \c headerData(). For TableModel to be editable, it has to provide implementations \c insertRows(), \c removeRows(), \c setData() and \c flags() functions. \snippet itemviews/addressbook/tablemodel.h 0 Two constructors are used, a default constructor which uses \c TableModel's own \c {QList>} and one that takes \c {QList} as an argument, for convenience. \section1 TableModel Class Implementation We implement the two constructors as defined in the header file. The second constructor initializes the list of pairs in the model, with the parameter value. \snippet itemviews/addressbook/tablemodel.cpp 0 The \c rowCount() and \c columnCount() functions return the dimensions of the model. Whereas, \c rowCount()'s value will vary depending on the number of contacts added to the address book, \c columnCount()'s value is always 2 because we only need space for the \bold Name and \bold Address columns. \note The \c Q_UNUSED() macro prevents the compiler from generating warnings regarding unused parameters. \snippet itemviews/addressbook/tablemodel.cpp 1 The \c data() function returns either a \bold Name or \bold {Address}, based on the contents of the model index supplied. The row number stored in the model index is used to reference an item in the list of pairs. Selection is handled by the QItemSelectionModel, which will be explained with \c AddressWidget. \snippet itemviews/addressbook/tablemodel.cpp 2 The \c headerData() function displays the table's header, \bold Name and \bold Address. If you require numbered entries for your address book, you can use a vertical header which we have hidden in this example (see the \c AddressWidget implementation). \snippet itemviews/addressbook/tablemodel.cpp 3 The \c insertRows() function is called before new data is added, otherwise the data will not be displayed. The \c beginInsertRows() and \c endInsertRows() functions are called to ensure all connected views are aware of the changes. \snippet itemviews/addressbook/tablemodel.cpp 4 The \c removeRows() function is called to remove data. Again, \l{QAbstractItemModel::}{beginRemoveRows()} and \l{QAbstractItemModel::}{endRemoveRows()} are called to ensure all connected views are aware of the changes. \snippet itemviews/addressbook/tablemodel.cpp 5 The \c setData() function is the function that inserts data into the table, item by item and not row by row. This means that to fill a row in the address book, \c setData() must be called twice, as each row has 2 columns. It is important to emit the \l{QAbstractItemModel::}{dataChanged()} signal as it tells all connected views to update their displays. \snippet itemviews/addressbook/tablemodel.cpp 6 The \c flags() function returns the item flags for the given index. \snippet itemviews/addressbook/tablemodel.cpp 7 We set the Qt::ItemIsEditable flag because we want to allow the \c TableModel to be edited. Although for this example we don't use the editing features of the QTableView object, we enable them here so that we can reuse the model in other programs. The last function in \c {TableModel}, \c getList() returns the QList> object that holds all the contacts in the address book. We use this function later to obtain the list of contacts to check for existing entries, write the contacts to a file and read them back. Further explanation is given with \c AddressWidget. \snippet itemviews/addressbook/tablemodel.cpp 8 \section1 AddressWidget Class Definition The \c AddressWidget class is technically the main class involved in this example as it provides functions to add, edit and remove contacts, to save the contacts to a file and to load them from a file. \snippet itemviews/addressbook/addresswidget.h 0 \c AddressWidget extends QTabWidget in order to hold 10 tabs (\c NewAddressTab and the 9 alphabet group tabs) and also manipulates \c table, the \c TableModel object, \c proxyModel, the QSortFilterProxyModel object that we use to filter the entries, and \c tableView, the QTableView object. \section1 AddressWidget Class Implementation The \c AddressWidget constructor accepts a parent widget and instantiates \c NewAddressTab, \c TableModel and QSortFilterProxyModel. The \c NewAddressTab object, which is used to indicate that the address book is empty, is added and the rest of the 9 tabs are set up with \c setupTabs(). \snippet itemviews/addressbook/addresswidget.cpp 0 The \c setupTabs() function is used to set up the 9 alphabet group tabs, table views and proxy models in \c AddressWidget. Each proxy model in turn is set to filter contact names according to the relevant alphabet group using a \l{Qt::CaseInsensitive}{case-insensitive} QRegExp object. The table views are also sorted in ascending order using the corresponding proxy model's \l{QSortFilterProxyModel::}{sort()} function. Each table view's \l{QTableView::}{selectionMode} is set to QAbstractItemView::SingleSelection and \l{QTableView::}{selectionBehavior} is set to QAbstractItemView::SelectRows, allowing the user to select all the items in one row at the same time. Each QTableView object is automatically given a QItemSelectionModel that keeps track of the selected indexes. \snippet itemviews/addressbook/addresswidget.cpp 1 The QItemSelectionModel class provides a \l{QItemSelectionModel::selectionChanged()}{selectionChanged} signal that is connected to \c{AddressWidget}'s \c selectionChanged() signal. This signal to signal connection is necessary to enable the \gui{Edit Entry...} and \gui{Remove Entry} actions in \c MainWindow's Tools menu. This connection is further explained in \c MainWindow's implementation. Each table view in the address book is added as a tab to the QTabWidget with the relevant label, obtained from the QStringList of groups. \image addressbook-signals.png Signals and Slots Connections We provide 2 \c addEntry() functions: 1 which is intended to be used to accept user input, and the other which performs the actual task of adding new entries to the address book. We divide the responsibility of adding entries into two parts to allow \c newAddressTab to insert data without having to popup a dialog. The first \c addEntry() function is a slot connected to the \c MainWindow's \gui{Add Entry...} action. This function creates an \c AddDialog object and then calls the second \c addEntry() function to actually add the contact to \c table. \snippet itemviews/addressbook/addresswidget.cpp 2 Basic validation is done in the second \c addEntry() function to prevent duplicate entries in the address book. As mentioned with \c TableModel, this is part of the reason why we require the getter method \c getList(). \snippet itemviews/addressbook/addresswidget.cpp 3 If the model does not already contain an entry with the same name, we call \c setData() to insert the name and address into the first and second columns. Otherwise, we display a QMessageBox to inform the user. \note The \c newAddressTab is removed once a contact is added as the address book is no longer empty. Editing an entry is a way to update the contact's address only, as the example does not allow the user to change the name of an existing contact. Firstly, we obtain the active tab's QTableView object using QTabWidget::currentWidget(). Then we extract the \c selectionModel from the \c tableView to obtain the selected indexes. \snippet itemviews/addressbook/addresswidget.cpp 4a Next we extract data from the row the user intends to edit. This data is displayed in an instance of \c AddDialog with a different window title. The \c table is only updated if changes have been made to data in \c aDialog. \snippet itemviews/addressbook/addresswidget.cpp 4b \image addressbook-editdialog.png Screenshot of Dialog to Edit a Contact Entries are removed using the \c removeEntry() function. The selected row is removed by accessing it through the QItemSelectionModel object, \c selectionModel. The \c newAddressTab is re-added to the \c AddressWidget only if the user removes all the contacts in the address book. \snippet itemviews/addressbook/addresswidget.cpp 5 The \c writeToFile() function is used to save a file containing all the contacts in the address book. The file is saved in a custom \c{.dat} format. The contents of the QList of \l{QPair}s are written to \c file using QDataStream. If the file cannot be opened, a QMessageBox is displayed with the related error message. \snippet itemviews/addressbook/addresswidget.cpp 6 The \c readFromFile() function loads a file containing all the contacts in the address book, previously saved using \c writeToFile(). QDataStream is used to read the contents of a \c{.dat} file into a list of pairs and each of these is added using \c addEntry(). \snippet itemviews/addressbook/addresswidget.cpp 7 \section1 NewAddressTab Class Definition The \c NewAddressTab class provides an informative tab telling the user that the address book is empty. It appears and disappears according to the contents of the address book, as mentioned in \c{AddressWidget}'s implementation. \image addressbook-newaddresstab.png Screenshot of NewAddressTab The \c NewAddressTab class extends QWidget and contains a QLabel and QPushButton. \snippet itemviews/addressbook/newaddresstab.h 0 \section1 NewAddressTab Class Implementation The constructor instantiates the \c addButton, \c descriptionLabel and connects the \c{addButton}'s signal to the \c{addEntry()} slot. \snippet itemviews/addressbook/newaddresstab.cpp 0 The \c addEntry() function is similar to \c AddressWidget's \c addEntry() in the sense that both functions instantiate an \c AddDialog object. Data from the dialog is extracted and sent to \c AddressWidget's \c addEntry() slot by emitting the \c sendDetails() signal. \snippet itemviews/addressbook/newaddresstab.cpp 1 \image signals-n-slots-aw-nat.png \section1 AddDialog Class Definition The \c AddDialog class extends QDialog and provides the user with a QLineEdit and a QTextEdit to input data into the address book. \snippet itemviews/addressbook/adddialog.h 0 \image addressbook-adddialog.png \section1 AddDialog Class Implementation The \c AddDialog's constructor sets up the user interface, creating the necessary widgets and placing them into layouts. \snippet itemviews/addressbook/adddialog.cpp 0 To give the dialog the desired behavior, we connect the \gui OK and \gui Cancel buttons to the dialog's \l{QDialog::}{accept()} and \l{QDialog::}{reject()} slots. Since the dialog only acts as a container for name and address information, we do not need to implement any other functions for it. \section1 MainWindow Class Definition The \c MainWindow class extends QMainWindow and implements the menus and actions necessary to manipulate the address book. \table \row \o \inlineimage addressbook-filemenu.png \o \inlineimage addressbook-toolsmenu.png \endtable \snippet itemviews/addressbook/mainwindow.h 0 The \c MainWindow class uses an \c AddressWidget as its central widget and provides the File menu with \gui Open, \gui Close and \gui Exit actions, as well as the \gui Tools menu with \gui{Add Entry...}, \gui{Edit Entry...} and \gui{Remove Entry} actions. \section1 MainWindow Class Implementation The constructor for \c MainWindow instantiates AddressWidget, sets it as its central widget and calls the \c createMenus() function. \snippet itemviews/addressbook/mainwindow.cpp 0 The \c createMenus() function sets up the \gui File and \gui Tools menus, connecting the actions to their respective slots. Both the \gui{Edit Entry...} and \gui{Remove Entry} actions are disabled by default as such actions cannot be carried out on an empty address book. They are only enabled when one or more contacts are added. \snippet itemviews/addressbook/mainwindow.cpp 1a \dots \codeline \snippet itemviews/addressbook/mainwindow.cpp 1b Apart from connecting all the actions' signals to their respective slots, we also connect \c AddressWidget's \c selectionChanged() signal to its \c updateActions() slot. The \c openFile() function allows the user to choose a file with the \l{QFileDialog::getOpenFileName()}{open file dialog}. The chosen file has to be a custom \c{.dat} file that contains address book contacts. This function is a slot connected to \c openAct in the \gui File menu. \snippet itemviews/addressbook/mainwindow.cpp 2 The \c saveFile() function allows the user to save a file with the \l{QFileDialog::getSaveFileName()}{save file dialog}. This function is a slot connected to \c saveAct in the \gui File menu. \snippet itemviews/addressbook/mainwindow.cpp 3 The \c updateActions() function enables and disables \gui{Edit Entry...} and \gui{Remove Entry} depending on the contents of the address book. If the address book is empty, these actions are disabled; otherwise, they are enabled. This function is a slot is connected to the \c AddressWidget's \c selectionChanged() signal. \snippet itemviews/addressbook/mainwindow.cpp 4 \section1 main() Function The main function for the address book instantiates QApplication and opens a \c MainWindow before running the event loop. \snippet itemviews/addressbook/main.cpp 0 */