Improvements - Constructor

1
Constructors

• Improvements - Constructor
• Parameter passing

Problem Solving With C
2
Example Point Class

• This is an ADT to store and manipulate the
  location of a single point on a two-dimensional
  plane.

3
Point Class (cond)

• Two modification member functions
• Shifting function
• Example B obtained by shifting point A by 1.3
  units along the X axis and by -1.4 units along
  the Y axis

Y
A (-1, 0.8)
X
4
Point Class (cond)

• Two modification member functions
• Shifting function
• Example B obtained by shifting point A by 1.3
  units along the X axis and by -1.4 units along
  the Y axis

Y
A (-1, 0.8)
X
B (0.3, -0.8)
5
Point Class (cond)

• Two modification member functions (cond)
• Rotating function
• Example C obtained by rotating point A by 90
  degree clockwise.

Y
A (-1, 0.8)
X
6
Point Class (cond)

• Two modification member functions (cond)
• Rotating function
• Example C obtained by rotating point A by 90
  degree clockwise.

Y
C (0.8, 1.0)
A (-1, 0.8)
X
7
Point Class (cond)

• Two constant member functions
• return X coordinate of the point. double
  get_x() const
• return Y coordinate of the point double
  get_y() const

8
Point Class (cond)

• Class Point
• public
• void shift(double x_ammount, double y_ammount)
• void rotate90()
• double get_x() const return x
• double get_y() const return y
• private
• double x // x coordinate of this point
• double y // y coordinate of this point

Inline functions
9
Improvements Constructor

• A member function that is automatically called to
  initialize an object when the object is declared

10
Improvements Constructor

• A member function that is automatically called to
  initialize an object when the object is declared
• The name of the constructor must be the same as
  the name of the class

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Improvements Constructor

• A member function that is automatically called to
  initialize an object when the object is declared
• The name of the constructor must be the same as
  the name of the class
• It does not have any return value

12
Constructor (cond)

• Two kinds of constructors
• Default constructor constructor with no
  parameters
• Constructor with parameters
• Example Point Class

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Constructor (cond)

• Example Point Class

Class Point ... //Constructor Point( )
//or Point(double initial_x, double initial_y)

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Constructor (cond)

• Example Point Class
• Application
• Point pointA
• Point pointB(5, 10)

15
Constructor (cond)

• Example Point Class
• Application
• Point pointA
• Point pointB(5, 10)

If the constructor has parameters, then the
values must be given after the object name.
16
Constructor (cond)

• A good technique using constructor with default
  parameters
• Example Point Class
• PointPoint(double initial_x 0,
• double initial_y 0)

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Constructor (cond)
int main( ) Point pointA(5, 10) Point
pointB(5) Point pointC ... return
0

• When you declare an object, what happen to these
  declarations?

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Constructor (cond)

• When you declare an object, what happen to these
  declarations?

void main() Point pointA(5, 10) Point
pointB(5) Point pointC ...
Initial_x 5, initial_y 10
Initial_x 5 initial_y 0
Initial_x 0, initial_y 0
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Constructor (cond)

• What if you write a class without constructors?

20
Constructor (cond)

• What if you write a class without constructors?
• Automatic default constructor will be called