![Abstract property cannot be accessed in the constructor meaning Abstract property cannot be accessed in the constructor meaning](/uploads/1/2/5/4/125458511/741619045.jpg)
Objects cannot be created from an abstract class. The purpose of an abstract class is to provide an appropriate superclass from which other classes can inherit and share the same design. You make a class abstract by declaring it with keyword abstract. Abstract classes are used as superclasses in inheritance hierarchies.
TypeScript brings full class-based inheritance to JavaScript projects. This works very well, but you may run into some unexpected behavior when setting properties in a subclass and using those properties in the parent constructor.Here is a simple example that demonstrates the problem:. MyBaseClass is defined as an abstract class.
Like other OOP languages, this means that the class cannot be instantiated directly. MySubClass is a concrete subclass of MyBaseClass that can be instantiated. New in TypeScript 2.0 is the ability to define properties as abstract, which I have done with string1 and string2. These properties must be set in the subclass, or the transpiler will generate an error. The parent class constructor sets the string3 property based on the values of string1 and string2 set in the subclass.
Imagine that string3 is a property that will be used by other methods in the base class (not shown in the example code), so it is a valid design choice to set that property in the constructor. Finally, the last two lines of code instantiate the class and display string3.
Inheritance (C# Programming Guide). 7 minutes to read.In this articleInheritance, together with encapsulation and polymorphism, is one of the three primary characteristics of object-oriented programming. Inheritance enables you to create new classes that reuse, extend, and modify the behavior that is defined in other classes. The class whose members are inherited is called the base class, and the class that inherits those members is called the derived class. A derived class can have only one direct base class. However, inheritance is transitive. If ClassC is derived from ClassB, and ClassB is derived from ClassA, ClassC inherits the members declared in ClassB and ClassA.