CategoryOOP

Inheritance

Inheritance

What exactly is Inheritance? MSDN explanation says : 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.

So what can we inherit? For example we have Car and Motorcycle classes, and as we know cars and motorcycles have a few things in common such as engine and color. We could create a base class named Vehicle that has those properties and make Car and Motorcycle classes which will inherit Vehicle class.

 

Can i inherit from multiple classes? No, but you can Inherit multiple Interfaces that inherit one class.

 

I don’t wish for my class or method to be directly instantiated. What can I do about that problem? You can make those classes or methods abstract. Beware, when you make your class abstract one, none of your class members have to be marked as abstract, but if at least one of your members is marked as abstract, entire class must be marked as abstract.

 

Can derived class access private fields of base class? No, it can not. You can only access internal, public, protected, and protected internal members of a base class.

 

Is it possible to prevent our class from becoming other classes base class? Yes, mark that class as sealed and other classes cannot inherit from this class.

Properties

It is good practice to keep our fields private but so far we had to create at least two methods to access or change their values.

 

Why not star using properties? You consume properties as fields and write them (almost) as methods.

Simple property example:

 

But why stop there we can add more functionality to our properties, like set our string name to Upercase, return default value or check if integer is a positive number.

 

A property that has both accessors is read-write property. Properties with only get accessor are called read-only properties, properties with only get accessor are called write-only properties.

 

When you only need basic property without any additional logic, you could create auto-implemented property without filed (actually compiler creates one for you).

Simple isn’t it 🙂

Encapsulation example

In our encapsulation example we will create 3 classes:

Color

Car

And Manufacturer

 

In color Class there will be 2 private read-only fields containing colors and two public methods to access them. Fields will be private read-only because we do not want someone to access or change their values, and methods will be public because we want to access values from our fields.

 

Car class will also contain 2 private fields but with car model names and two public methods which can access our fields, but we will also create two public static integers whose values we will access and alter in Manufacturer class.

 

Manufacturer class will access methods from Color and Car classes and alter one of static integers from Car class.

Encapsulation example:

 

 

 

Encapsulation

Encapsulation is one of main four object-oriented programming concepts. Encapsulation is part of OOP where we decide on which depth level another user (programmer) can can dig in our code. Encapsulation is implemented by using access modifiers.

List of access modifiers:

  • Public
  • Private
  • Protected
  • Internal
  • Protected internal

Public access modifier allows a class to expose its variables and methods to other classes/methods/objects/etc.. inside and and outside of it’s original class even outside of original assembly.

Private access modifier is default access modifier, meaning if we do not specify access modifier explicitly private is set as default one. Only methods of the same class can access its private members, meaning an instance of a class cannot access its private members L.

Protected and Protected internal access modifier are mostly used in implementing inheritance (one of the pillars of OOP). They allow child class to access variables and methods of base class. These access modifier will be explained later in Inheritance chapter.

Internal access modifier, same as public but is limited only to its root assembly. Internal is default access modifier of classes.

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