1. Programming with ANSI C ++
A Step-by-Step Approach
Prof. Bhushan Trivedi
Director
GLS Institute of Computer Technology

2. Chapter 5 Constructors and Destructors

3. Constructors and Destructors
The similar-to-built-in behavior concept
The Need for initialization of objects
Default initializing data members
When dynamic memory allocation is required
Setting values at the time of declaration
Inheritance

4. Introduction to constructors
What constructor does?
Automatically Initialize the object
Set the values at the time of initialization
The COMPILER GENERATED CONSTRUCTOR myth
The Trivial and non Trivial cases

5. The Rules for Constructors
Same name as the class!
Can not specify a return type
Can not have return statement
More constructors must overload
Can not the either const or volatile
Address can not be obtained
Private constructors are special

6. Introduction to constructors
The C++ default construction and relation to constructors
Compiler generated default constructor
The need for user defined default constructor
The programmers responsibility and the implementation’s need
When not having default constructor can make program misbehave

7. Constructors with one parameter & =
class Number {}; main() { Number No2; No2 = 5; /* this is implicit conversion. 5 is converted to Number object and then assigned to No2*/ }

8. Conversion The implicit conversion
The explicit constructors prevent the unexpected conversion

9. Categorizing Parameterized constructors Having multiple constructors
Constructors with default arguments
Dynamic initialization and assignment using explicit call to constructor function at run time
Constructors with dynamic allocation

10. An Explicit Call Constructor can be explicitly called!
Object O(val) Object O= Val and Object O = object (val) forms are all same
It does return the Object of the class it is constructor of!
It can make the object assigned to other values then it initialized with

11. Constructor with dynamic allocation
When we assign memory dynamically for initializing an object, it is our job to de-allocate them, when the object goes out of scope. Unlike the case of other variables, where C++ does de-allocation as soon as the variable goes out of scope, here it is not done until the program execution is over. This problem is known as memory leak.

12. The need of copy constructors
Constructor can not have native objects as arguments
Difference between Object initialization and Object Assignment
The three cases when CC is needed
Initializing other then default way
Passing an argument to a function
Returning an object from a function

13. The need of copy constructors,
Object Initialization and assignment are different
Copy constructor needed when object is to be initialized while assignment operator is to be overloaded for assignment
Private Copy constructors for stopping a copy

14. The member initialization list
The need for initialization list:
Readability
Efficiency
Only way to initialize for const, references and classes
Using initialization list in place of statements in the body of constructor function

15. The member initialization list
The order of initialization
The initialization and assignment
Difference is important here as well
Assignment is always after the initialization

16. Destructors The need for destructors Usage
when the dynamic constructor used to construct the object
When the termination effect is to be provided
Assignment operator, copy constructor and destructors are all three needed together usually

17. Other issues
Constructors and Destructors are special for const Objects
Constructors executed anytime before the object is really used in the program
Destructors are executed when the object goes out of scope
The lifetime of an object is from time when the constructor execution is over till destructor execution begins