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Why do we need sealed classes in Kotlin?
Kotlin has support for using sealed classes in its when constructs. Because there are always an exact set of possible subclasses, the compiler is able to warn us if any branch is not handled, in exactly the same way that it does for enumerations.
What is use of sealed class?
Sealed classes are used to restrict the users from inheriting the class. A class can be sealed by using the sealed keyword. The keyword tells the compiler that the class is sealed, and therefore, cannot be extended. No class can be derived from a sealed class.
Can sealed class be extended Kotlin?
Kotlin has a great feature called sealed class, which allow us to extend an abstract class in a set of fixed concrete types defined in the same compilation unit (a file). In other words, is not possible to inherit from the abstract class without touching the file where it is defined.
Why are classes sealed?
The main purpose of a sealed class is to take away the inheritance feature from the class users so they cannot derive a class from it. One of the best usage of sealed classes is when you have a class with static members. For example, the Pens and Brushes classes of the System.
Can you instantiate a sealed class?
Sealed classes and interfaces represent restricted class hierarchies that provide more control over inheritance. A sealed class is abstract by itself, it cannot be instantiated directly and can have abstract members.
Can we declare abstract class as sealed?
When a class is declared sealed, it cannot be inherited, abstract classes cannot be declared sealed. To prevent being overridden, use the sealed in C#.
What is sealed method?
Prevent overriding a method of a class. This is a method that is declared with the keyword sealed and is always used with combination of override keyword. Derived classes will not be able to override this method as it is sealed for overriding.
Can we use sealed class with abstract class?
If any class contains abstract methods then it must be declared by using the keyword abstract. An abstract class can contain sealed methods. The abstract method or class cannot be declared as sealed.
How do I extend my class with Kotlin?
Kotlin provides the ability to extend a class with new functionality without having to inherit from the class or use design patterns such as Decorator. This is done via special declarations called extensions. For example, you can write new functions for a class from a third-party library that you can’t modify.
Can a sealed class inherit from another class?
A Sealed Class is a class where we cannot derive or create a new class. In other words, the Sealed Class can’t be inherited by other classes and by using a sealed modifier we can also define a class that is declared called Sealed Class.