8.1: Introduction to Object Oriented Programming (PC Users)
- Page ID
- 128177
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Object-oriented programming (OOP) is a computer programming approach that uses classes and objects. In object-oriented programming, we first create classes and then use classes to create objects. Such objects posses certain features and functions that can be used in a program.
As an example, here we create a class called Rectangle and then we use this class to create objects in a program.
To create a class, we will need to open a header file (a file with .h as its file extension)
To create a header file:
1. Open a project
Select "Empty Project" and then click on "Next":
Name the project, and then click on "Create"
when a project is open, In Solution Explorer, right click on Header File (.h) -> Add -> New Item
Following window opens. In this window, select Heater File (.h) and name the file as Rectangle, then click on "Add":
Now, a blank header file, named as Rectangle.h, is open as following: (Delete the preloaded code if there is one)
Inside of this header file we will write a C++ class for creating rectangle objects. Now, following the steps below:
Step 1: Name the class as Rectangle and separate code of the class with two sections, private and public shown as follows:
Step 2: Declare two data members under the private section and declare six member functions in the public section as shown below:
Two data members specify the attributes of a rectangle and member functions specify the functionalities of the class Rectangle. This portion of the class is called class interface or class definition.
Now, we continue the header file with the implementations of those member functions specified in the class interface. Implementing a member function is to code the function based on its functionality. For example, the first member function is for setting the numerical value for the length of a rectangle, we implement this function as follows:
This function has no return value, we specify the function with void. This function is one of the member functions of the class Rectangle, we place the code Rectangle:: in front of the header of the function. The function has only one input specified by double len. This function contains a single line of the code: length=len; which is setting the value of the length to the input value of the function len.
Similarly, we implement the rest of the member functions as following:
In following program, we demonstrate how to use the class Rectangle to create objects and how to call the member functions of the class Rectangle.
Line 2: #include"Rectangle.h" links the header file Rectangle.h to the program.
Line 7: Here we use the class Rectangle to create an object myRec. In other words, myRec is an instance of the class Rectangle. myRec posses all the functions we specified in the class definition.
Line 8 and Line 9: We are calling setLength() and setWidth() functions that come with the instance myRec to set the numerical values for the length and the width of myRec.
Line 10: We are calling the member function of myRec.display() to visualize the instance myRec.
Line 11: We are calling member function getArea() to calculate and return the value of the area of the instance myRec.
Following is the screen shot of a test run of the program:
