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