Flutter for Beginners

Abstract classes

In OOP, abstract classes are classes that cannot be instantiated, which makes a lot of sense, depending on the context and the level of abstraction in a program.

For example, our Person class could be abstract if we want to make sure that it only exists in the context of the program if it is a Student instance or another subtype:

abstract class Person {  // ... the body was hidden for brevity}

The only thing we need to change here is the beginning of the class definition, marking it as abstract:

main() {  Person student = new Student("Clark", "Kent", "Kal-El"); // works as           //we are instantiating the subtype     // Person p = new Person();   // abstract classes cannot be instantiated  print(student); }

As you can see, we can no ...