1. ECE 264 Object-Oriented Software Development
Instructor: Dr. Honggang Wang
Fall 2012
Lecture 37: Exam 3 Preview

2. Lecture outline Announcements/Reminders General exam information
Lab 10 submission due by tomorrow
Project demos due December 7 (Friday)
Entire group members must attend
Presentation order: Group 1-Group 4
Project documentation (user’s guide, tech report) due December 10
General exam information
Q & A Friday?
Exam review: what we’ve covered since the last exam (not an exhaustive list!)
Destructors
Copy constructors
Operator overloading
Inheritance
Basics of base/derived classes
Use of constructors
Virtual functions
Pure virtual functions & abstract classes
4/27/2017
ECE 264: Lecture 37

3. General exam information
8.5” x 11” double-sided sheet of notes allowed; paper based materials allowed
Exam date/time: Monday, 12/10, 9:00-9:50 am
Exam will be written to (hopefully) take one hour
Exam will be held in room: S&E 212
Very similar format to Exams 1 & 2: 3 questions, most of which have multiple parts
Question 1: Multiple choice (more ?s, fewer points per ?)
Question 2: Understanding code (i.e., given some code, what’s output?)
Question 3: Writing short code sequences
Sample Questions and solutions will be uploaded Tuesday
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ECE 264: Lecture 37

4. Review: Destructors class-name::~class-name() { }
Destructors called when object destroyed; used for “object cleanup”
At end of function
When delete is used to deallocate object
Often empty, unless object contains dynamically allocated data
Destructor is responsible for deleting that data
Syntax:
class-name::~class-name() { }
4/27/2017
ECE 264: Lecture 16

5. Review: Copy constructors
Called when new object created from existing object
Example: Point p2 = p1;
Default is shallow copy
Need deep copy if object contains
Array(s)
Dynamically allocated data
Must still copy all data members
Syntax:
class_name::class_name(const class_name &<param_name>)
Example:
tenInts::tenInts(const tenInts &t){
for (int i=0; i < 10; i++)
arr[i] = t.arr[i]; }
4/27/2017
ECE 264: Lecture 37

6. Review: Operator overloading
Allows use of built-in operators with user-defined types
Definitions for overloaded operators included in class definition
Example (from Point class)
double operator –(const Point& rhs);
Syntax:
Keyword operator is used, followed by the actual operator
“Argument” is an object reference of the same type
const declarations are optional but often preferred
Syntax exceptions: friend functions
Has access to class data, but not technically part of class
Used if LHS of operation is not of same type as class
Example: stream operators (e.g. cin >> h1;)
Both sides (of binary operator) must be specified as “arguments”
4/27/2017
ECE 264: Lecture 37

7. Review: Inheritance
Create new class (derived class) from existing class (base class)
Base class has functionality shared by derived class
Can add functions to derived class
Can customize base class functionality
Can have inheritance hierarchy
Syntax example using Rectangle/Square
In Square.h, declare class as:
class Square : public Rectangle
Default constructor for a base class is called automatically in the derived class constructor
Ex: Square() calls Rectangle()
Will actually traverse inheritance hierarchy, starting at lowest class
If derived class needs the parameterized constructor of base class, must explicitly invoke it in initialization list
Ex: Square::Square(const Point &p, double s) :
Rectangle(s, s, p.getX(), p.getY())
Access visibility: for data/functions to be visible to base & derived class(es), but not clients, declare as protected
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ECE 264: Lecture 37

8. Review: Polymorphism/virtual functions
Polymorphism: Code/operations behave differently in different contexts
One example: operator overloading
Inheritance-based polymorphism in form of virtual functions
Virtual functions allow us to write generic code that works for (hopefully) many specific cases
Using pointers to objects allows dynamic binding
Base class pointer can be used for derived class object
ptr->function() will call version for appropriate class
Also useful when
Passing function arguments by reference
Calling member function inside another member function (implicitly using this pointer)
Remember, a class with virtual functions should have a virtual destructor
4/27/2017
ECE 264: Lecture 37

9. Review: Abstract classes
Abstract classes give ability to specify generic class
At least some base class functionality is too general to implement  use pure virtual function
Having pure virtual function(s) makes class abstract
Cannot instantiate object of abstract class type
Pure virtual function syntax (in .h file):
virtual <return_type> <fname>(<args>) = 0;
Derived classes must overload pure virtual functions
Failure to do so makes derived class abstract!
4/27/2017
ECE 264: Lecture 37