03 Iec T1s1 Oops Session 04

Object-Oriented Programming Using C# Objectives In this session, you will learn to: Define abstraction and encapsulation Implement encapsulation by using access specifiers Use methods

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Object-Oriented Programming Using C# Introducing Abstraction and Encapsulation Abstraction and encapsulation are important features of any object-oriented programming language. Abstraction involves extracting only the relevant information. Encapsulation involves packaging one or more components together.

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Object-Oriented Programming Using C# Defining Abstraction An automobile salesperson is aware that different people have different preferences. Some people are interested in the speed of a car, some in its price, some in the engine, and the some in its style. Although all of them want to buy a car, each of them is interested in a specific attribute or feature. The salesman knows all the details of a car, but he presents only the relevant information to a potential customer. As a result, a the salesman practices abstraction and presents only relevant details to customer.

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Object-Oriented Programming Using C# Defining Encapsulation Encapsulation literally means ‘to enclose in or as if in a capsule’. Encapsulation is defined as the process of enclosing one or more items within a physical or logical package. It involves preventing access to nonessential details.

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Object-Oriented Programming Using C# Implementing Encapsulation by Using Access Specifiers An access specifier defines the scope of a class member. A class member refers to the variables and functions in a class. A program can have one or more classes. You may want some members of a class to be accessible to other classes. But, you may not want some other members of the class to be accessible outside the class.

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Object-Oriented Programming Using C# Types of Access Specifiers C# supports the following access specifiers: public private protected internal protected internal

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Object-Oriented Programming Using C# Demo: Calculating Area and Volume by Using Access Specifiers Problem Statement: Write a program to calculate the area of a rectangle and a square.

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Object-Oriented Programming Using C# Using Methods A method is a set of one or more program statements, which can be executed by referring to the method name. To use methods, you need to: Define methods Call methods

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Object-Oriented Programming Using C# Defining Methods Defining a method means declaring the elements of its structure. Consider the syntax of defining a method: <Method Name>(Parameter List) { Method Body }

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Object-Oriented Programming Using C# Defining Methods (Contd.) The elements of the method declaration include the method name, the parameters list, the return type, and the method body. The following are the elements of a method: Access specifier Return type Method name Parameter list Method body

Let us understand each of the element of the method declaration.

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Object-Oriented Programming Using C# Defining Methods (Contd.) Defining a method means declaring the elements of its structure. Consider the syntax of defining a method:

This determines the extent to which a variable or method can be accessed from another class. <Method Name>(Parameter List) { Method Body }

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Object-Oriented Programming Using C# Defining Methods (Contd.) Defining a method means declaring the elements of its structure. Consider the syntax of defining a method:

A method can return a value of any type. If the method is not returning any value, use void as the <Method Name>(Parameter List) return type. { Method Body }

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Object-Oriented Programming Using C# Defining Methods (Contd.) Defining a method means declaring the This is a unique elements of its structure. identifier and is Consider the syntax of defining a method: case-sensitive. The method name cannot be the <Method Name>(Parameter List) same as the { variable name or Method Body any other } non-method item declared in the class.

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Object-Oriented Programming Using C# Defining Methods (Contd.) Defining a method means declaring the This is used to elements of its structure. pass and receive Consider the syntax of defining a method: the data from a method. It is enclosed between <Method Name>(Parameter List) parentheses. The { parentheses are Method Body included even if } there are no parameters.

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Object-Oriented Programming Using C# Defining Methods (Contd.) Defining a method means declaring the elements of its structure. Consider the syntax of defining a method:

This contains the set of instructions needed to complete the required activity.

<Method Name>(Parameter List) { Method Body }

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Object-Oriented Programming Using C# Calling Methods After defining the method, you can execute it by calling it. You can call a method by using the name of the method. The method name is followed by parentheses even if the method call has no parameters, as shown in the following example: MethodName();

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Object-Oriented Programming Using C# Calling Methods (Contd.) The following is an example of calling methods: using System; class Calculator { public int AddNumber(int num1, int num2) { int result; result = num1 + num2; return result; } static void Main(string[] args)

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Object-Oriented Programming Using C# Calling Methods (Contd.) { Calculator cal = new Calculator(); // The following statement is calling the // AddNumber method and passing 10 and // 20 as the parameter list. int value=cal.AddNumber(10, 20); Console.WriteLine("The result is {0}", value); Console.ReadLine(); } }

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Object-Oriented Programming Using C# Using Methods with Parameters Methods can also be declared with parameters. Consider the example of declared a method with parameters: void DisplayResult (int result) { //….. }

When the methods are declared with parameters, they should be called with parameters. The methods with parameters are called by passing the value using the following mechanism: Value Reference Output

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Object-Oriented Programming Using C# Using Methods with Parameters (Contd.) Value: The parameters passed by value creates a separate copy in the memory. The following example shows the parameters passed by value: void CalculateSum( int num1, int num2) { //… } void Accept() { int val1=10; int val2=2; CalculateSum(val1,val2); }

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Object-Oriented Programming Using C# Using Methods with Parameters (Contd.) Reference: The parameters passed by reference does not creates a separate copy of the variable in the memory. A reference parameter stores the memory address of the data member passed. The following example shows the parameters passed by reference: void CalculateSum( ref int num1,ref int num2) { //… } void Accept() { int val1=10; int val2=2; CalculateSum( ref val1,ref val2); } Ver. 1.0

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Object-Oriented Programming Using C# Using Methods with Parameters (Contd.) Output: The output parameters are used to pass the value out of the method. The following example shows the parameters passed by reference: void CalculateSum( ref int num1,ref int num2, out int result) { result=num1+num2; } void Accept() { int val1=10; int val2=2; int recieveVal; CalculateSum( ref val1,ref val2,out recieveVal); } Ver. 1.0

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Object-Oriented Programming Using C# Demo: Swapping Two Numbers by Using Methods with Parameters Problem Statement: Write a program to swap two numbers by using reference type parameters in a method.

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Object-Oriented Programming Using C# Summary In this session, you learned that: Abstraction is the process of reducing information content in order to retain only the relevant information for a particular purpose. Encapsulation is the process of hiding all the details of an object that do not contribute to its essential characteristics. An access specifier is used to determine whether any other class or function can access the member variables and functions of a particular class. The public access specifier allows a class to expose its member variables and member functions to other functions and objects. The private access specifier allows a class to hide its member variables and member functions from other class functions and objects.

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Object-Oriented Programming Using C# Summary (Contd.) The protected access specifier allows a class to hide its member variables and member functions from other class objects and functions, just like the private access specifier while implementing inheritance. A method is a set of one or more program statements that can be executed by referring to the method name. Defining a method means declaring the elements of its structure. The access modifiers that can be used with methods are public, protected, internal, protected internal, and private. Parameters allow information to be passed into and out of a method. When you define a method, you can include a list of parameters in parentheses.

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Object-Oriented Programming Using C# Summary (Contd.) Parameters can be passed by using any one of the following parameters types: Value Reference Output

Pass by value is the default mechanism for passing parameters in C#. A reference parameter is a reference to a memory location of a data member. Output parameters are like reference parameters, except that they transfer data out of the method rather than into it. The return statement is used to return the control to the caller.

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