**Course Title:** Qt 6 Application Development with C++ **Section Title:** Advanced Widgets and Custom Forms **Topic:** Building an advanced form with custom validation and reusable widgets.(Lab topic) **Introduction** In this lab topic, we will create an advanced form that incorporates custom validation and reusable widgets. We will apply the concepts we have learned so far, including working with Qt widgets, layouts, and signals. By the end of this topic, you will be able to create complex forms that meet specific requirements. **Prerequisites** Before starting this lab topic, ensure you have a good understanding of the following concepts: * Working with Qt widgets, layouts, and signals * Creating reusable custom widgets using inheritance and composition * Advanced signal-slot management and custom signals **Step 1: Define the Form Requirements** For this lab, we will create a "User Registration Form" that includes the following fields: * First name * Last name * Email address * Password * Confirm password The form should also have the following validation rules: * First name and last name should not be empty * Email address should be in a valid format * Password should be at least 8 characters long and contain at least one uppercase letter and one lowercase letter * Confirm password should match the password **Step 2: Create the Form UI** Open Qt Creator and create a new project. Choose "Applications" under the "Projects" section and select "Qt Widgets Application". Create a new QWidget class that will serve as the base class for our form. Call it `UserRegistrationForm`. ```cpp // userregistrationform.h #ifndef USERREGISTRATIONFORM_H #define USERREGISTRATIONFORM_H #include <QWidget> namespace Ui { class UserRegistrationForm; } class UserRegistrationForm : public QWidget { Q_OBJECT public: explicit UserRegistrationForm(QWidget *parent = nullptr); ~UserRegistrationForm(); private: Ui::UserRegistrationForm *ui; }; #endif // USERREGISTRATIONFORM_H ``` ```cpp // userregistrationform.cpp #include "userregistrationform.h" #include "ui_userregistrationform.h" UserRegistrationForm::UserRegistrationForm(QWidget *parent) : QWidget(parent), ui(new Ui::UserRegistrationForm) { ui->setupUi(this); } UserRegistrationForm::~UserRegistrationForm() { delete ui; } ``` **Step 3: Create Custom Validator for Email Address** Create a new class `EmailValidator` that will validate the email address. ```cpp // emailvalidator.h #ifndef EMAILVALIDATOR_H #define EMAILVALIDATOR_H #include <QValidator> class EmailValidator : public QValidator { public: EmailValidator(QObject *parent = nullptr); State validate(QString &input, int &pos) const override; }; #endif // EMAILVALIDATOR_H ``` ```cpp // emailvalidator.cpp #include "emailvalidator.h" #include <QRegExp> EmailValidator::EmailValidator(QObject *parent) : QValidator(parent) { } EmailValidator::State EmailValidator::validate(QString &input, int &pos) const { QRegExp rx("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$"); if (rx.indexIn(input) != -1) { return Valid; } return Invalid; } ``` **Step 4: Create Custom Validator for Password** Create a new class `PasswordValidator` that will validate the password. ```cpp // passwordvalidator.h #ifndef PASSWORDVALIDATOR_H #define PASSWORDVALIDATOR_H #include <QValidator> class PasswordValidator : public QValidator { public: PasswordValidator(QObject *parent = nullptr); State validate(QString &input, int &pos) const override; }; #endif // PASSWORDVALIDATOR_H ``` ```cpp // passwordvalidator.cpp #include "passwordvalidator.h" #include <QRegExp> PasswordValidator::PasswordValidator(QObject *parent) : QValidator(parent) { } PasswordValidator::State PasswordValidator::validate(QString &input, int &pos) const { QRegExp rx("^(?=.*[a-z])(?=.*[A-Z]).{8,}$"); if (rx.indexIn(input) != -1) { return Valid; } return Invalid; } ``` **Step 5: Apply Custom Validators** Apply the custom validators to the email address and password fields. ```cpp // userregistrationform.cpp #include "userregistrationform.h" #include "ui_userregistrationform.h" #include "emailvalidator.h" #include "passwordvalidator.h" UserRegistrationForm::UserRegistrationForm(QWidget *parent) : QWidget(parent), ui(new Ui::UserRegistrationForm) { ui->setupUi(this); EmailValidator *emailValidator = new EmailValidator(this); ui->emailLineEdit->setValidator(emailValidator); PasswordValidator *passwordValidator = new PasswordValidator(this); ui->passwordLineEdit->setValidator(passwordValidator); ui->confirmPasswordLineEdit->setValidator(passwordValidator); } ``` **Step 6: Connect Signals** Connect the signals from the form fields to slots that will perform the validation. ```cpp // userregistrationform.cpp #include "userregistrationform.h" #include "ui_userregistrationform.h" UserRegistrationForm::UserRegistrationForm(QWidget *parent) : QWidget(parent), ui(new Ui::UserRegistrationForm) { ui->setupUi(this); connect(ui->firstNameLineEdit, &QLineEdit::textChanged, this, &UserRegistrationForm::validateFirstName); connect(ui->lastNameLineEdit, &QLineEdit::textChanged, this, &UserRegistrationForm::validateLastName); connect(ui->emailLineEdit, &QLineEdit::textChanged, this, &UserRegistrationForm::validateEmail); connect(ui->passwordLineEdit, &QLineEdit::textChanged, this, &UserRegistrationForm::validatePassword); connect(ui->confirmPasswordLineEdit, &QLineEdit::textChanged, this, &UserRegistrationForm::validateConfirmPassword); } void UserRegistrationForm::validateFirstName() { 秦ui->firstNameLineEdit->text(); } void UserRegistrationForm::validateLastName() { Qinui->lastNameLineEdit->text(); } void UserRegistrationForm::validateEmail() { Qinui->emailLineEdit->text(); } void UserRegistrationForm::validatePassword() { 秦ui->passwordLineEdit->text(); } void UserRegistrationForm::validateConfirmPassword() { Qinui->confirmPasswordLineEdit->text(); } ``` **Conclusion** In this lab topic, we created an advanced form that includes custom validation and reusable widgets. We applied the concepts we learned throughout this course to create a complex form that meets specific requirements. You can now create your own advanced forms using the skills and knowledge you have gained. **Additional Resources** * Qt Documentation: [QValidator](https://doc.qt.io/qt-6/qvalidator.html) * Qt Documentation: [QRegExp](https://doc.qt.io/qt-6/qregexp.html) * Stack Overflow: [How to validate email address in Qt](https://stackoverflow.com/questions/18473834/how-to-validate-email-address-in-qt) **Leave a Comment/Ask for Help** If you have any questions or need help with this lab topic, please leave a comment below. **Next Topic** In the next topic, we will cover "Designing dynamic UIs that respond to window resizing" from the section "Building Responsive and Dynamic UIs".