Instance Variables & Instance Methods in Dart

Instance variable is a variable which declared inside the class but outside any function.
Instance method is a method which declared inside the class but outside any function.
- In below example we can see that we have crated on class called Student and inside the call we have declare two variable which is " Id and name ",
  
  This two variable called in instance variable.
- While we create three function in this class which are study , sleep and Alldetails , this three function called Instance Method.
- For calling the class we use object , here we have use student1 as object and we call this object to call class variable and method to get output.

void main() {


    //Using object to call
    var student1 = Student();         // One Object, student1 is reference variable
    student1?.id = 01;
    student1?.name = "Vinit";
    student1?.Alldetails();
    student1?.study();
    student1?.sleep();


}

// Define states (properties) and behavior of a Student
class Student {
    int? id ;             // Instance Variable, default value is null


    String? name;          // Instance Variable, default value is null


    //Instance Method
    void study() {
        print("${this.name} is now studying");
    }

    //Instance Method
    void sleep() {
        print("${this.name} is now sleeping");
    }

  //Instance Method
   void Alldetails()
  {
    print("$id is $name");
  }
}