Abstract Class, Abstract Function and Abstract Property in Kotlin скачать в хорошем качестве

Abstract Class, Abstract Function and Abstract Property in Kotlin

If you want to prevent a class from being instantiated, you can mark the class as abstract by prefixing it with the abstract keyword. A class that’s not abstract is called concrete. An abstract class can have abstract properties and functions. An abstract class can contain abstract and non-abstract properties and functions. It’s possible for an abstract class to have no abstract members. Abstract properties and functions don’t need to be marked as open. If you mark a property or function as abstract, you must mark the class as abstract too. If you put even one abstract property or function in a class, you have to mark the class as abstract or your code won’t compile. Abstract properties and functions define a common protocol so that you can use polymorphism. Inheritable function implementations (functions with actual bodies) are useful to put in a superclass when it makes sense. And in an abstract class, it often doesn’t make sense because you may not be able to come up with any generic code that the subclasses would find useful. Abstract functions are useful because even though they don’t contain any actual function code, they define the protocol for a group of subclasses which you can use for polymorphism. How to implement an abstract class? You declare that a class inherits from an abstract superclass in the same way that you say that a class inherits from a normal superclass: by adding a colon to the class header followed by the name of the abstract class. You implement abstract properties and functions by overriding each one and providing an implementation. This means that you need to initialize any abstract properties, and you need to provide a body for any abstract functions. When you implement abstract properties and functions, you must follow the same rules for overriding that you use for overriding normal properties and functions: When you implement an abstract property, it must have the same name, and its type must be compatible with the type defined in the abstract superclass. In other words, it must be the same type, or one of its subtypes. When you implement an abstract function, it must have the same function signature (name and arguments) as the function that’s defined in the abstract superclass. Its return type must be compatible with the declared return type. You MUST implement all abstract properties and functions. Every property and function in a concrete class must be implemented so that the compiler knows what to do when they’re accessed. Only abstract classes can have abstract properties or functions. If a class has any properties or functions that are marked as abstract, the entire class must be abstract. When a subclass inherits from an abstract superclass, the subclass can still define its own functions and properties. Key Characteristics and Rules Cannot be Instantiated: You can never create an instance of an abstract class directly using AbstractClassName(). Must be Inherited: To use the functionality defined within an abstract class, you must create a concrete subclass that inherits from it. Contains Abstract Members: Abstract classes can declare abstract members (properties and functions) that do not have an implementation in the base class. Subclasses Must Implement: Any non-abstract subclass must provide concrete implementations for all abstract members defined in the parent abstract class. Open by Default: Unlike normal Kotlin classes (which are final by default), abstract classes are implicitly open. You do not need to explicitly use the open keyword on an abstract class itself. Abstract Members are Open: Similarly, abstract functions and properties are also implicitly open, allowing them to be overridden in subclasses. Telegram Group: https://t.me/androidNinjaWarrior Guide to watch: 00:00 What is abstract? 02:05 How to create abstract class in kotlin? 05:05 How to override abstract function in kotlin? 09:00 How to create and override abstract property in kotlin? 14:42 How to handle constructor in abstract class in kotlin? #Abstractions #Abstract #AbstractClass #AbstractMember #AbstractProperty #AbstractMethod #AbstractFunction #OverrideAbstractFunction #seriousPolymorphism #Polymorphism #Kotlin #KotlinCourse Disclaimer- Some content are used for educational purposes under fair use. Copyright Disclaimer Under Section 107 of the Copyright Act 1976, allowance is made for "fair use" for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational, or personal use tips the balance in favor of fair use. All credit for copyright material used in the video goes to the respected Owner. Thank you guys.