Plab Tirgul 6 Classes

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Plab Tirgul 6Classes
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Point.h
class Point public Point(int x, int
y) Point() int getX() const int
getY() constprivate int m_x, m_y
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Circle.h
include "Point.h class Circle public
Circle(int x, int y, double r)
Circle() // ... private Point
m_center // ...
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Circle.cpp
include "Circle.h CircleCircle(int x, int y,
double r) m_center(x,y) // ...
CircleCircle() printf(in
Circle()")
Wont compile without
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• The same syntax also works for base
  types.PointPoint(int x, int y) m_x(x) ,
  m_y(y) is better than
• PointPoint(int x, int y) m_x x
  m_y y

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Inheritance

• The main ideas are similar to what you already
  know from Java.
• C has no interfaces but it allows multiple
  inheritance
• For now we will not discuss the problems that
  arise

Class A
Class C
Class B
Class D
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Circle class - again
include "Point.h class Circle Point public
Circle(int x, int y, double r)
Circle() // ...
private // ...
include "Circle.h CircleCircle(int x, int y,
double r) Point(x,y) // ...
CircleCircle() printf(in
Circle()")
Wont compile without
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Default arguments in constructors

• In C
• PointPoint(int x 0, int y 0) //
  ...
• is equivalent to JavasPoint(int x, int y) . .
  .Point(int x) this(x,0) Point()
  this(0,0)
• Note that now Point has a default constructor!

Nothing similar in C
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C-tor D-tor order of execution

• Constructor of the base class is the 1st to be
  executed.
• Then the members are constructed.
• Finally, the constructor of the class itself is
  executed.
• Destruction is done in the opposite order.

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protected

• Class members that should be accessible by
  subclasses are declared protected.
• Example to allow Circle access coordinates of
  Point we would define

class Point public // . . . protected
int m_x, m_y
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this

• A (constant) pointer to the instance for which
  the member function was invoked.
• Example

class List List nextpublic bool
on(List) // ...
bool Liston(List p) if (pnull)
return false for (List q this q
qq-gtnext) if (q p) return true
return false
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inline functions

• A hint to a compiler to put functions code
  inline, rather than perform a regular function
  call.
• Objective improve performance of small,
  frequently used functions.
• Example allocateNode() function in data
  structures like Linked List or Binary Tree.
• A member function defined in class definition
  (i.e. the header file) is automatically
  considered to be inline.
• An inline function defined in .cpp file is not
  recognized in other source files.

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Static class members

• As in Java, these are members belonging to the
  class rather than to an instance.

class X private static int instances
public X() instances X()
instances-- static int getInstances()
return instances
X.h
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Static class members
Somewhere (but only in one place!) the instances
variable should be defined int Xinstances 0
In Java declaration and defintion were in the
same place
Example of using a static function X x1 //
... X x2 // ... printf(d\n,
XgetInstances())