declaring a class: the.h file #pragma once #include using namespace std; class student { private:...

Declaring a Class: the .h file

#pragma once

#include <string>

using namespace std;

class Student

{

private:

string myFirst;

string myLast;

int myCredits;

double myGPA;

string myClassYear;

public:

Student(void);

Student(string, int, double);

~Student(void);

void setMyFirst(string);

void setMyLast(string);

void setMyGpa(double);

void setMyClassYear(string);

string getMyFirst(void);

string getMyLast(void);

int getMyCredits(void);

double getMyGPA(void);

string getMyClassYear(void);

void addCredits(int);

string toString(void);

};

Implementing a class:the .cpp file

#include "Student.h"

#include <sstream>

Student::Student(void)

{

myName = "None";

myCredits = 0;

myGPA = 0.0;

myClassYear = "None";

}

Student::Student(string fisrt, string last,

int credits, double gpa)

{

myFirst = first;

myLast = last;

myCredits = credits;

myGPA = gpa;

if (myCredits >= 92)

myClassYear = "Senior";

else if (myCredits >= 60)

myClassYear = "Junior";


myClassYear = "Sophomore";

else

myClassYear = "Freshman";

}

.cpp file continuedvoid Student::setMyFirst(string first)

{ myFirst = first; }

void Student::setMyLast(string last)

{ myLast = last; }

void Student::setMyGpa(double gpa)

{ myGPA = gpa; }

void Student::setMyClassYear(string year)

{ myClassYear = year; }

string Student::getMyFirst(void)

{ return myFirst; }

String Student::getMyLast(void)

{ return myLast; }

int Student::getMyCredits(void)

{ return myCredits; }

double Student::getMyGPA(void)

{ return myGPA; }

string Student::getMyClassYear(void)

{ return myClassYear; }

.cpp file continued

• void Student::addCredits(int credits)• {• if (credits > 0)• {• myCredits = myCredits + credits;• if (myCredits >= 92)• myClassYear = "Senior";• else if (myCredits >= 60)• myClassYear = "Junior";• else if (myCredits >= 28)• myClassYear =

"Sophomore";• else• myClassYear = "Freshman";• }• }

.cpp continued

string Student::toString(void)

{

stringstream credits, gpa;

credits << myCredits;

gpa << myGPA;

string c, g;

c = credits.str();

g = gpa.str();

string stuString = "Name: " + myLast +

“, “ + myFirst +

"\nCredits: " + c +

"\nGPA: " + g +

"\nClass: " +

myClassYear +

"\n";

return stuString;

}

Constructor Method• A constructor is a special method

that assigns initial values to instance variables.1. Constructors must have the same name as the class itself.2. Constructors do not have a return type—not even void.3. Constructors are invoked when an object is created.

• The constructor is automatically called whenever an object is created.

Student’s Default Constructor

Student::Student(void)

{

myFirst = "None";

myLast = “None”;

myCredits = 0;

myGPA = 0.0;

myClassYear = "None";

}

A class normally provides a constructor without formal parameters (arguments) (e.g., Student(void)).

• #include "Student.h"• #include <iostream>• #include <string>• using namespace std;

• int main ()• {• Student sue;• cout << "Name " << sue.getMyLast() • << endl;• cout << "Credits " • << sue.getMyCredits() << endl;• cout << "GPA " << sue.getMyGPA() • << endl;• cout << "Year " • << sue.getMyClassYear() << endl;• return 0;• }

Default constructor in action

Assign Class Year from Credits

Credits Class Year

>= 92 Senior

>= 60 Junior

>= 28 Sophomore

0-27 Freshman

Initializing Constructor

• This version of the constructor method receives parameters that are used to set the initial instance variable values.

• For class Student: pre-conditions: receives:– String for setting name– int for setting credit hours earned– double for setting GPA

Initializing Constructor

• Add this constructor after the default Student() constructor method.

• The name of this method is also Student

• Pre-conditions: Receives– string for specifying name– int for giving the credit hours earned– double for giving the GPA

Student’s Initializing Constructor

Student::Student(string last, string first,

int credits, double gpa)

{

myFirst = first;

myLast = last;

myCredits = credits;

myGPA = gpa;







else


}


#include <iostream>

#include <string>


int main ()

{

Student sue("Doe","Sue", 16, 4.0);

cout << "Name " << sue.getMyLast()

<< “, “ << sue.getMyFirst << endl;

cout << "Credits "

<< sue.getMyCredits() << endl;

cout << "GPA " << sue.getMyGPA()

<< endl;

cout << "Year "

<< sue.getMyClassYear() << endl;

return 0;

}

Initializing Constructor in Action

• Declare another Student object named Joe.

• Use the initializing constructor to create and initialize instance variables for your new Student with a name of “Joe”, credits of 60 and a gpa of 3.8.

• Use accessors to retrieve and print out all of its instance variable values.

Using the Initializing Constructor


#include <iostream>

#include <string>


int main ()

{

Student joe(“Blow”,"Joe", 32, 3.92);

cout << "Name " << joe.getMyLast()

<< “, “ << joe.getMyFirst

<< endl;

cout << "Credits "

<< joe.getMyCredits() << endl;

cout << "GPA " << joe.getMyGPA()

<< endl;

cout << "Year "

<< joe.getMyClassYear()

<< endl;

return 0;

}

Initializing Constructor in Action

Printing a Student’s Data

• Wouldn’t it be easier if our main didn’t have to call four “getter” methods and do four cout commands to get and display a Student’s information.

• What could we add to class Student to help save us from doing all these steps?

toString Method

• Write public method inside class Student

• Pre-conditions: None

• Post-conditions: prints out the value of each Student attribute with appropriate messages.

toString Method

string Student::toString(void)

{

stringstream credits, gpa;

credits << myCredits;

gpa << myGPA;

string c, g;

c = credits.str();

g = gpa.str();

string stuString = "Name: " + myLast +

“, “ + myFirst +

"\nCredits: " + c +

"\nGPA: " + g +

"\nClass: " + myClassYear +

"\n";

return stuString;

}

toString in action


#include <iostream>

#include <string>


int main ()

{


cout << joe.toString();

}

• Pre-condition: Receives an integer value giving number of credits earned.

• Post-conditions: If given number of credits is > 0, then add that number of credits to the Student’s credits instance variable. Returns updated number of credit hours.

addCredits Method

Student’s addCredits Method

void Student::addCredits(int credits)

{

if (credits > 0)

{

myCredits = myCredits + credits;







else


}

}


#include <iostream>

#include <string>


int main ()

{


joe.addCredits(16);

cout << joe.toString();

}

Using addCredits Method

declaring a class: the.h file #pragma once #include using namespace std; class student { private:...

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