Explains how to add edit and remove functionality.
Now we look at ways to modify the contents of contacts stored in the address book.
We now have an address book that not only holds contacts in an organized manner, but also allows navigation. It would be convenient to include edit and remove functions so that a contact's details can be changed when needed. However, this requires a little improvement, in the form of enums. We defined two modes:
AddingMode
and
NavigationMode
, but they were not defined as enum values. Instead, we enabled and disabled the corresponding buttons manually, resulting in multiple lines of repeated code.
Here we define the
模式
enum with three different values:
NavigationMode
,
AddingMode
，和
EditingMode
.
addressbook.h
file is updated to contain the
模式
枚举：
enum Mode { NavigationMode, AddingMode, EditingMode };
We also add two new slots,
editContact()
and
removeContact()
, to our current list of public slots.
void editContact();
void removeContact();
In order to switch between modes, we introduce the
updateInterface()
function to control the enabling and disabling of all
QPushButton
objects. We also add two new push buttons,
editButton
and
removeButton
, for the edit and remove functions mentioned earlier.
void updateInterface(Mode mode);
...
QPushButton *editButton;
QPushButton *removeButton;
...
Mode currentMode;
Lastly, we declare
currentMode
to keep track of the enum's current mode.
We now implement the mode-changing features of the address book. The
editButton
and
removeButton
are instantiated and disabled by default. The address book starts with zero contacts in memory.
editButton = new QPushButton(tr("&Edit"));
editButton->setEnabled(false);
removeButton = new QPushButton(tr("&Remove"));
removeButton->setEnabled(false);
These buttons are then connected to their respective slots,
editContact()
and
removeContact()
, and we add them to
buttonLayout1
.
connect(editButton, &QPushButton::clicked,
this, &AddressBook::editContact);
connect(removeButton, &QPushButton::clicked,
this, &AddressBook::removeContact);
...
buttonLayout1->addWidget(editButton);
buttonLayout1->addWidget(removeButton);
editContact()
function stores the contact's old details in
oldName
and
oldAddress
, before switching the mode to
EditingMode
. In this mode, the
submitButton
and
cancelButton
are both enabled, hence, the user can change the contact's details and click either button.
void AddressBook::editContact() { oldName = nameLine->text(); oldAddress = addressText->toPlainText(); updateInterface(EditingMode); }
submitContact()
function has been divided in two with an
if-else
statement. We check
currentMode
to see if it's in
AddingMode
. If it is, we proceed with our adding process.
void AddressBook::submitContact() { ... if (currentMode == AddingMode) { if (!contacts.contains(name)) { contacts.insert(name, address); QMessageBox::information(this, tr("Add Successful"), tr("\"%1\" has been added to your address book.").arg(name)); } else { QMessageBox::information(this, tr("Add Unsuccessful"), tr("Sorry, \"%1\" is already in your address book.").arg(name)); }
Otherwise, we check to see if
currentMode
是在
EditingMode
. If it is, we compare
oldName
with
名称
. If the name has changed, we remove the old contact from
contacts
and insert the newly updated contact.
} else if (currentMode == EditingMode) {
if (oldName != name) {
if (!contacts.contains(name)) {
QMessageBox::information(this, tr("Edit Successful"),
tr("\"%1\" has been edited in your address book.").arg(oldName));
contacts.remove(oldName);
contacts.insert(name, address);
} else {
QMessageBox::information(this, tr("Edit Unsuccessful"),
tr("Sorry, \"%1\" is already in your address book.").arg(name));
}
} else if (oldAddress != address) {
QMessageBox::information(this, tr("Edit Successful"),
tr("\"%1\" has been edited in your address book.").arg(name));
contacts[name] = address;
}
}
updateInterface(NavigationMode);
}
If only the address has changed (i.e.,
oldAddress
is not the same as
address
), we update the contact's address. Lastly, we set
currentMode
to
NavigationMode
. This is an important step as it re-enables all the disabled push buttons.
To remove a contact from the address book, we implement the
removeContact()
function. This function checks to see if the contact exists in
contacts
.
void AddressBook::removeContact() { QString name = nameLine->text(); QString address = addressText->toPlainText(); if (contacts.contains(name)) { int button = QMessageBox::question(this, tr("Confirm Remove"), tr("Are you sure you want to remove \"%1\"?").arg(name), QMessageBox::Yes | QMessageBox::No); if (button == QMessageBox::Yes) { previous(); contacts.remove(name); QMessageBox::information(this, tr("Remove Successful"), tr("\"%1\" has been removed from your address book.").arg(name)); } } updateInterface(NavigationMode); }
If it does, we display a
QMessageBox
, to confirm the removal with the user. Once the user has confirmed, we call
previous()
to ensure that the user interface shows another contact, and we remove the contact using
QMap
's
remove()
function. As a courtesy, we display a
QMessageBox
to inform the user. Both the message boxes used in this function are shown below:
We mentioned the
updateInterface()
function earlier as a means to enable and disable the push buttons depending on the current mode. The function updates the current mode according to the
mode
argument passed to it, assigning it to
currentMode
before checking its value.
Each of the push buttons is then enabled or disabled, depending on the current mode. The code for
AddingMode
and
EditingMode
展示如下：
void AddressBook::updateInterface(Mode mode) { currentMode = mode; switch (currentMode) { case AddingMode: case EditingMode: nameLine->setReadOnly(false); nameLine->setFocus(Qt::OtherFocusReason); addressText->setReadOnly(false); addButton->setEnabled(false); editButton->setEnabled(false); removeButton->setEnabled(false); nextButton->setEnabled(false); previousButton->setEnabled(false); submitButton->show(); cancelButton->show(); break;
For
NavigationMode
, however, we include conditions within the parameters of the
QPushButton::setEnabled
() function. This is to ensure that
editButton
and
removeButton
are enabled when there is at least one contact in the address book;
nextButton
and
previousButton
are only enabled when there is more than one contact in the address book.
case NavigationMode:
if (contacts.isEmpty()) {
nameLine->clear();
addressText->clear();
}
nameLine->setReadOnly(true);
addressText->setReadOnly(true);
addButton->setEnabled(true);
int number = contacts.size();
editButton->setEnabled(number >= 1);
removeButton->setEnabled(number >= 1);
nextButton->setEnabled(number > 1);
previousButton->setEnabled(number >1 );
submitButton->hide();
cancelButton->hide();
break;
}
}
By setting the mode and updating the user interface in the same function, we avoid the possibility of the user interface getting out of sync with the internal state of the application.