Overloaded Constructors in Computer Science II
Dr. Katherine Gibson's lecture covers topics related to overloaded constructors in Computer Science II for Majors. The content also includes important exam rules, disability services information, and exam formats and tips for students at UMBC. It emphasizes the significance of exam integrity, preparation strategies, and coding best practices.
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CMSC202 Computer Science II for Majors Lecture 08 Overloaded Constructors Dr. Katherine Gibson www.umbc.edu Based on slides by Chris Marron at UMBC
Student Disability Services If you need to take the exam at SDS: You need to set it up with them You need to make sure I know about it This needs to be done ahead of time This should already have been done by now! 2 www.umbc.edu
Exam Rules The exam is closed everything: No books No notes No cheat sheets No laptops No calculators No phones 3 www.umbc.edu
Exam Rules Place your bookbag under your desk/chair NOT on the seat next to you You may have on your desk: Pens, pencils, erasers Water bottle UMBC ID 4 www.umbc.edu
Exam Rules DO NOT CHEAT!!! Cheating will be dealt with severely and immediately If a TA or instructor sees you looking at another student s paper (or anything other than your own exam) they will take your test from you Space allowing, you will sit every other seat, so that you are not next to another student 5 www.umbc.edu
Exam Format True/False Multiple Choice Short Answer Explain basic concepts in writing Debugging Find and correct errors 6 www.umbc.edu
Exam Format Code Evaluations Given code, what does it do? Code Completions Given a partial piece of code Correctly fill in blanks to complete code Coding Problems Given a problem, write code to solve it 7 www.umbc.edu
Exam Tips: General Write down your name and circle your section Flip through the exam and get a feel for the length of it and the types of questions If a problem is unclear or you think there is an error on the exam, raise your hand Most questions have partial credit You should at least attempt every problem 8 www.umbc.edu
Exam Tips: Coding When coding: Read the question carefully Plan out what your code needs to do After you are done coding the programming problems, try running your program with some input and making sure it works the way you think it does 9 www.umbc.edu
Exam Content Everything we ve covered so far! Including... C++ Syntax Loops, data types, cin, cout, C-strings, etc. Functions Prototype, definition, call, return value, parameters Pointers, arrays Passing arrays to functions, &, *, addresses, etc. Classes! Access modifiers, class methods, member variables, constructors, objects, dot operator And more! 10 www.umbc.edu
Questions about Exam 1? www.umbc.edu
Last Class We Covered Classes Access modifiers Methods Mutators Accessors Facilitators Constructors Livecoding: Rectangle class 12 www.umbc.edu
Any Questions from Last Time? www.umbc.edu
Todays Objectives To learn about overloading methods Regular class methods Overloaded constructors To complete our Rectangle class To review for Exam 1 14 www.umbc.edu
Overloading www.umbc.edu
Overloading We can define multiple versions of the constructor we can overload it Different constructors for: When all values are known When no values are known When some subset of values are known 16 www.umbc.edu
All Known Values Have the constructor set user-supplied values Date::Date (int m, int d, int y) { SetMonth(m); SetDay(d); SetYear(y); } invoked when constructor is called with all arguments 17 www.umbc.edu
No Known Values Have the constructor set all default values invoked when constructor is called with no arguments Date::Date () { SetMonth(DEFAULT_MON); SetDay(DEFAULT_DAY); SetYear(DEFAULT_YEAR); } 18 www.umbc.edu
Some Known Values Have the constructor set some default values Date::Date (int m, int d) { SetMonth(m); SetDay(d); SetYear(DEFAULT_YEAR); } invoked when constructor is called with two arguments 19 www.umbc.edu
Overloaded Date Constructor so far we have the following constructors: Date::Date (int m, int d, int y); Date::Date (int m, int d); Date::Date (); would the following be a valid constructor? Date::Date (int m, int y); 20 www.umbc.edu
Avoiding Multiple Constructors Defining multiple constructors for different sets of known values is a lot of unnecessary code duplication We can avoid this by setting default parameters in our constructors 21 www.umbc.edu
Default Parameters In the function prototype only, provide default values you want the constructor to use Date (int m , int d , int y ); 22 www.umbc.edu
Default Parameters In the function prototype only, provide default values you want the constructor to use Date (int m = 1, int d = 12, int y = 1967); (You should, of course, use constants when providing default parameters.) 23 www.umbc.edu
Default Parameters In the function definition nothing changes Date::Date (int m, int d, int y) { SetMonth(m); SetDay(d); SetYear(y); } 24 www.umbc.edu
Using Default Parameters the following are all valid declarations: Date graduation(5,19,2016); Date gritBDay; Date halloween(10,31); Date july(4); NOTE: when you call a constructor with no arguments, you do not give it empty parentheses // graduation: 5/19/2016 // gritBDay: 1/12/1967 // halloween: 10/31/1967 // july: 4/12/1967 25 www.umbc.edu
Default Constructors A default constructor is provided by compiler Will handle declarations of Date instances This is how we created Date objects in the slides before we declared and defined our constructor 26 www.umbc.edu
Default Constructors But, if you create any other constructor, the compiler doesn t provide a default constructor So if you create a constructor, make a default constructor too, even if its body is just empty Date::Date () { /* empty */ } 27 www.umbc.edu
Function Overloading Functions in C++ are uniquely identified by both their names and their parameters But NOT their return type! We can overload any kind of function We can even use default values, like with constructors 28 www.umbc.edu
Overloading Example void PrintMessage (void) { cout << "Hello World!" << endl; } void PrintMessage (string msg) { cout << msg << endl; } 29 www.umbc.edu
Time for LIVECODING!!! 30 www.umbc.edu
Livecoding Exercise Update our Rectangle class with Overloaded Constructor Implemented through default parameters Create a class method to: Print all of a Rectangle s information Update our main() function 31 www.umbc.edu
Announcements Project 1 is due tonight by 9:00 PM Make sure you have correctly submitted all of your files! Exam 1 will be held on Thursday (the 25th) during our regular class time 32 www.umbc.edu
