在flutter中调用类并访问类对象

class Person {
  String name;
  int age;

  Person(this.name, this.age);

  void greet() {
    print('Hello, my name is $name and I am $age years old.');
  }
}

void main() {
  // 创建Person类的实例
  Person person = Person('Alice', 30);

  // 访问对象的属性
  print(person.name); // 输出: Alice
  print(person.age);  // 输出: 30

  // 调用对象的方法
  person.greet(); // 输出: Hello, my name is Alice and I am 30 years old.
}

class Person {
  String name;
  int age;

  Person(this.name, this.age);

  void greet() {
    if (name == null || age == null) {
      throw Exception('Name and age must be initialized.');
    }
    print('Hello, my name is $name and I am $age years old.');
  }
}

void greet() {
  if (name != null && age != null) {
    print('Hello, my name is $name and I am $age years old.');
  } else {
    print('Name or age is not initialized.');
  }
}