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This C++ code outlines the declaration and implementation of a `Student` class. The class includes member variables such as name, credits, GPA, and class year. It features both a default constructor and an initializing constructor for setting student attributes at the time of object creation. The class provides methods for getting and setting the various attributes, adding credits, and converting the student's information into a string format. The implementation demonstrates encapsulation and the use of access modifiers within C++.
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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"; else if (myCredits >= 28) myClassYear = "Sophomore"; else myClassYear = "Freshman"; }
.cpp file continued void 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)).
Default constructor in action • #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; • }
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; if (myCredits >= 92) myClassYear = "Senior"; else if (myCredits >= 60) myClassYear = "Junior"; else if (myCredits >= 28) myClassYear = "Sophomore"; else myClassYear = "Freshman"; }
Initializing Constructor in Action #include "Student.h" #include <iostream> #include <string> using namespace std; 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; }
Using the Initializing Constructor • 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.
Initializing Constructor in Action #include "Student.h" #include <iostream> #include <string> using namespace std; 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; }
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 "Student.h" #include <iostream> #include <string> using namespace std; int main () { Student joe(“Blow”,"Joe", 32, 3.92); cout << joe.toString(); }
addCredits Method • 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.
Student’s addCredits Method 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"; } }
Using addCredits Method #include "Student.h" #include <iostream> #include <string> using namespace std; int main () { Student joe(“Blow”,"Joe", 32, 3.92); joe.addCredits(16); cout << joe.toString(); }
