1. Classes

2. Warmup class Thing { public: void foo(int a) {cout << “A”;}
void foo(double a) {cout << “B”;} };
int main()
Thing a();
a.foo(1); }
What will this script output?

3. Warmup 2 void foo() { cout << “B”; } class Thing { public:
void foo() {cout << “A”;}
void bar() {foo();} };
int main()
Thing a();
a.bar();
What will this script output?

4. Header Files
In order to promote reusability of code, it is common to put user-defined classes and functions into header files.
This way if another person wants to reuse classes or functions, they can simply include the header file.
This is done using
#include “filename.h”
which pastes the contents of the file filename.h into a program

5. Separating Interface and Implementation
It is also common to put declarations into a .h file and put the associated definitions into .cpp file of the same name.
If we define a Person class, we would be the declarations into a person.h file and the definitions into a person.cpp file. We would include person.h in our person.cpp file

6. Header Files
Always put #pragma once at the beginning of a header file. Otherwise, if multiple files include the header file in a project, there are redefinition problems.
Alternatively can put
#ifndef FILENAME_H
#define FILENAME_H
at the start and
#endif
at the end

7. Problem: Implementing a Date class
Suppose we wanted to implement a class which represents dates, e.g., 10/23/1997.
Things to consider when designing this class:
What data variables would we want an object of this class to have?
What methods should an object of this class have?

8. Problem: Date Class
Implement a Date class which has 3 data variables (day, month, year) and the following methods
A constructor that accepts three input variables (corresponding to the month, day, and year)
A default constructor that accepts no input variables and sets the date to 1/1/1970
One accessor function for each of our private data variables.
A mutator function that inputs three variables (corresponding to the day, month, and year) and sets the stored date equal to that input.
A procedure that prints the stored date to the console in the format MM/DD/YYYY.

9. Problem: Equality Testing
Write a method for Date equals which accepts a Date object and returns true if they are equal.
Date date1(1,6,1999), date2(1,7,1999);
date1.equals(date2) // should be false
What should the header of the method look like?
What should be in the body?
Why can’t we just do date1 == date2?

10. Operator Overloading: ==
We can define == for our Date class.
bool Date::operator==(const Date &date) const {
return equals(date); }