Part 2 - Adding Addresses#
Describes the code for inserting records in the Address Book Example.
The next step in creating the address book is to implement some user interactions.
We will provide a push button that the user can click to add a new contact. Also, some form of data structure is needed to store these contacts in an organized way.
Defining the AddressBook Class#
Now that we have the labels and input fields set up, we add push buttons to complete the process of adding a contact. This means that our
addressbook.h file now has three
QPushButton objects declared and three corresponding public slots.
slots: = public() def addContact(): def submitContact(): def cancel():
A slot is a function that responds to a particular signal. We will discuss this concept in further detail when implementing the
AddressBook class. However, for an overview of Qt’s signals and slots concept, you can refer to the Signals and Slots document.
QPushButton objects (
cancelButton) are now included in our private variable declarations, along with
# private addButton = QPushButton() submitButton = QPushButton() cancelButton = QPushButton() nameLine = QLineEdit() addressText = QTextEdit()
We need a container to store our address book contacts, so that we can traverse and display them. A
contacts, is used for this purpose as it holds a key-value pair: the contact’s name as the key, and the contact’s address as the value.
QString> = QMap<QString,() oldName = QString() oldAddress = QString()
We also declare two private
oldAddress. These objects are needed to hold the name and address of the contact that was last displayed, before the user clicked Add. So, when the user clicks Cancel, we can revert to displaying the details of the last contact.
Implementing the AddressBook Class#
Within the constructor of
AddressBook, we set the
addressText to read-only, so that we can only display but not edit existing contact details.
... nameLine.setReadOnly(True) ... addressText.setReadOnly(True)
Then, we instantiate our push buttons:
addButton = QPushButton(tr("Add")) addButton.show() submitButton = QPushButton(tr("Submit")) submitButton.hide() cancelButton = QPushButton(tr("Cancel")) cancelButton.hide()
addButton is displayed by invoking the
show() function, while the
cancelButton are hidden by invoking
hide() . These two push buttons will only be displayed when the user clicks Add and this is handled by the
addContact() function discussed below.
addButton.clicked.connect( self.addContact) submitButton.clicked.connect( self.submitContact) cancelButton.clicked.connect( self.cancel)
We connect the push buttons’
clicked() signal to their respective slots. The figure below illustrates this.
Next, we arrange our push buttons neatly to the right of our address book widget, using a
QVBoxLayout to line them up vertically.
buttonLayout1 = QVBoxLayout() buttonLayout1.addWidget(addButton, Qt.AlignTop) buttonLayout1.addWidget(submitButton) buttonLayout1.addWidget(cancelButton) buttonLayout1.addStretch()
addStretch() function is used to ensure the push buttons are not evenly spaced, but arranged closer to the top of the widget. The figure below shows the difference between using
addStretch() and not using it.
We then add
addLayout() . This gives us nested layouts as
buttonLayout1 is now a child of
mainLayout = QGridLayout() mainLayout.addWidget(nameLabel, 0, 0) mainLayout.addWidget(nameLine, 0, 1) mainLayout.addWidget(addressLabel, 1, 0, Qt.AlignTop) mainLayout.addWidget(addressText, 1, 1) mainLayout.addLayout(buttonLayout1, 1, 2)
Our layout coordinates now look like this:
addContact() function, we store the last displayed contact details in
oldAddress. Then we clear these input fields and turn off the read-only mode. The focus is set on
nameLine and we display
def addContact(self): oldName = nameLine.text() oldAddress = addressText.toPlainText() nameLine.clear() addressText.clear() nameLine.setReadOnly(False) nameLine.setFocus(Qt.OtherFocusReason) addressText.setReadOnly(False) addButton.setEnabled(False) submitButton.show() cancelButton.show()
submitContact() function can be divided into three parts:
We extract the contact’s details from
addressTextand store them in
QStringobjects. We also validate to make sure that the user did not click Submit with empty input fields; otherwise, a
QMessageBoxis displayed to remind the user for a name and address.def submitContact(self): name = nameLine.text() address = addressText.toPlainText() if name.isEmpty() or address.isEmpty(): QMessageBox.information(self, tr("Empty Field"), tr("Please enter a name and address.")) return
We then proceed to check if the contact already exists. If it does not exist, we add the contact to
contactsand we display a
QMessageBoxto inform the user that the contact has been added.if not contacts.contains(name): contacts.insert(name, address) QMessageBox.information(self, tr("Add Successful"), tr("\"%1\" has been added to your address book.").arg(name)) else: QMessageBox.information(self, tr("Add Unsuccessful"), tr("Sorry, \"%1\" is already in your address book.").arg(name)) return
If the contact already exists, again, we display a
QMessageBoxto inform the user about this, preventing the user from adding duplicate contacts. Our
contactsobject is based on key-value pairs of name and address, hence, we want to ensure that key is unique.
Once we have handled both cases mentioned above, we restore the push buttons to their normal state with the following code:if contacts.isEmpty(): nameLine.clear() addressText.clear() nameLine.setReadOnly(True) addressText.setReadOnly(True) addButton.setEnabled(True) submitButton.hide() cancelButton.hide()
The screenshot below shows the
QMessageBox object we use to display information messages to the user.
cancel() function restores the last displayed contact details and enables
addButton, as well as hides
def cancel(self): nameLine.setText(oldName) nameLine.setReadOnly(True) addressText.setText(oldAddress) addressText.setReadOnly(True) addButton.setEnabled(True) submitButton.hide() cancelButton.hide()
The general idea behind adding a contact is to give the user the flexibility to click Submit or Cancel at any time. The flowchart below further explains this concept: