Class Method Readclass Student{private: string id; string firstName, lastName; float gpa;

public:

// Will the method change any data members? // Yes! void Read() { cin >> id >> firstName >> lastName >> gpa; }

};

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Class Method Writeclass Student{private: string id; string firstName, lastName; float gpa;

public:

// Will the method change any data members? // NO! void Write() { cout << setw(6) << id << setw(15) << firstName << setw(15) << lastName << setw(8) << gpa; }

};2

Class Method Modifier constclass Student{private: string id; string firstName, lastName; float gpa;Public: // The method will NOT change any data members: const. void Write() const { cout << setw(6) << id << setw(15) << firstName << setw(15) << lastName << setw(8) << gpa; } // The method will change data members: no const. void Read() { cin >> id >> firstName >> lastName >> gpa; }}; 3

Class Method Modifier constclass Student{private: string id; string firstName, lastName; float gpa;public: void Write() const

float getGPA() const

string getFirst() const

// No const void Read() void setGPA( float value ) void updateGPA( float amount ) . . .};

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Comparing Objects

Student s1, s2;

// Input datas1.Read();s2.Read();

//Comparing GPAs of s1 and s2if (s1.getGPA() > s2.getGPA()) cout << s1.getFirst() << “ has higher GPA.”;else if (s1.getGPA() < s2.getGPA()) cout << s2.getFirst() << “ has higher GPA.”;else cout << s1.getFirst() << “ has the same GPA as ” << s2.getFirst();

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Comparing GPA without getGPAStudent s1, s2;

// Input datas1.Read();s2.Read();

//Comparing GPAs of s1 and s2if ( ? ) cout << s1.getFirst() << “ has higher GPA.”;else if ( ? ) cout << s2.getFirst() << “ has higher GPA.”;else cout << s1.getFirst() << “ has the same GPA as ” << s2.getFirst();

Need a New Method!

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Class Method HasHigherGPAThanclass Student{private: string id; string firstName, lastName; float gpa;public: //float getGPA() const string getFirst() const void Read()

bool HasHigherGPAThan( Student s ) { if ( gpa > s.gpa ) return true; else return false; }};

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Class Method HasHigherGPAThanclass Student{private: string id; string firstName, lastName; float gpa;public:/* Correct but not good. bool HasHigherGPAThan( Student s ) { if ( gpa > s.gpa ) return true; else return false; }*/ // Much better! bool HasHigherGPAThan( Student s ) { return gpa > s.gpa; }};

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Comparing GPA without getGPAStudent s1, s2;

// Input datas1.Read();s2.Read();

// Comparing GPAs of s1 and s2if ( s1.HasHigherGPAThan(s2) ) cout << s1.getFirst() << “ has higher GPA.”;else if (s2.HasHigherGPAThan(s1) ) cout << s2.getFirst() << “ has higher GPA.”;else cout << s1.getFirst() << “ has the same GPA as ” << s2.getFirst();

Don’t know the gpa of s1 or s2!

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Class Method HasHigherGPAThanclass Student{private: string id; string firstName, lastName; float gpa;public:

// Does it change any data member? // NO! bool HasHigherGPAThan( Student s ) { return gpa > s.gpa; }};

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Class Method HasHigherGPAThanclass Student{private: string id; string firstName, lastName; float gpa;public:

// Will not change any data member: const bool HasHigherGPAThan( Student s ) const { return gpa > s.gpa; }};

Passing Object as Parameter.

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Passing Parameters• Basic Data Types (char, int, float, string, bool) Pass by Value (without & in prototype) Pass by Reference (with & in prototype)• Arrays (of any data type) Always Pass by Reference (Never &)• Class Object (and structure) C++ allows pass by value (no &) and by reference (&) Our Rule: Always pass by reference with & Use const for in parameter

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Passing Object as Parameterclass Student{private: string id; string firstName, lastName; float gpa;

public: // Will not change any data member: const // Will not change parameter s: const with & bool HasHigherGPAThan( const Student& s ) const { return gpa > s.gpa; }};

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Passing Object as Parameterclass Student{private: string id; string firstName, lastName; float gpa;public:

// Copy constructor: // gets initial values from object s // Will change data members: no const. // Will not change parameter s: const with & Student( const Student& s) { id = s.id; firstName = s.firstName; lastName = s.lastName; gpa = s.gpa; }};

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Array of Objectsconst int MAX_SIZE = 35;

int numStudents;

// 35 floatsfloat scores[MAX_SIZE];

// 35 StudentsStudent students[MAX_SIZE];

// Single class objectStudent s;

Each array element of students[] is the same as variable s.

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Array of Objectsconst int MAX_SIZE = 35;

int numStudents;

Student s, students[MAX_SIZE];

// Input datas.Read();students[0].Read();

// Output datas.Write();students[1].Write();

// Update GPAs.UpdateGPA(0.2);students[index].UpdateGPA(0.5);

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const int MAX_SIZE = 35;

class Student{

};

int main(){ int numStudents; Student s, students[MAX_SIZE];

cin >> numStudents;

for (int i = 0; i < numStudents; i ++) students[i].Read();

. . .

return 0;}

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Using a function to read data to an array of Student

Function PrototypeFunction Name InputToStudentArray

Function Type void

Parameters s[] : array of Student size: int, number of students of s[]

// Parameters: (Out, Out)void InputToStudentArray(Student s[], int& size);

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//--------------------------------------------------// The function inputs value of size and then reads // data for size students into array s[].// Parameters: (Out, Out)//--------------------------------------------------void InputToStudentArray(Student s[], int& size){ cin >> size; for (int i = 0; i < size; i++) s[i].Read();

return;}

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//--------------------------------------------------// The function displays data of size students// of array s[].// Parameters: (In, In)//--------------------------------------------------void PrintStudentArray(const Student s[], int size){ for (int i = 0; i < size; i++) s[i].Write();

return;}

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//--------------------------------------------------// The function returns the index of the first // array element of s[] that has the same// firstName and lastName as student m.// Parameters: (In, In, In)//--------------------------------------------------int FindStudent(const Student s[], int size, const Student& m){ for (int i = 0; i < size; i++) if (s[i].getFirst() == m.getFirst() && s[i].getLast() == m.getLast()) return i;

return -1;}

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const int MAX_SIZE = 35;

class Student{

};

void InputToStudentArray(Student s[], int& size);void PrintStudentArray(const Student s[], int size);int FindStudent(const Student s[], int size, const Student& m);

int main(){

. . .

return 0;}

// Function definitions

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void InputToStudentArray(Student s[], int& size);void PrintStudentArray(const Student s[], int size);int FindStudent(const Student s[], int size, const Student& m);

int main(){ int numStudents, index; Student students[MAX_SIZE];

InputToStudentArray(students, numStudents);

PrintStudentArray(students, numStudents);

Student s(“Qi”, “Yang”, 2.9);

index = FindStudent(students, numStudents, s);

students[index].UpdateGPA(1.0);

PrintStudentArray(students, numStudents);

return 0;}

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Schedule

• Quiz7-2: Due Wednesday

• Program 5Pairs by Friday

• Lab 9Thursday

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