Object-Oriented Programming

1
Object-Oriented Programming

• C -- Ryan Graczyk

2
Introduction

• Classification of C according to its support of
  Object-Orientation
• C and Java are programming languages that were
  designed to support object-oriented programming
  and do not support other programming paradigms,
  but still employ some of the basic imperative
  structures. among such languages. Smalltalk is
  the only pure object-oriented language.

3
Single Inheritance

• Classes can inherit from another class. This is
  accomplished by putting a colon after the class
  name when declaring the class, and naming the
  class to inherit fromthe base classafter the
  colon
• public class A
• public A()
• public class B A
• public B()
• The new classthe derived classthen gains all
  the non-private data and behavior of the base
  class in addition to any other data or behaviors
  it defines for itself.
• Class B is effectively both B and A. When you
  access a B object, you can use the cast operation
  to convert it to an A object. The B object is not
  changed by the cast, but your view of the B
  object becomes restricted to A's data and
  behaviors. After casting a B to an A, that A can
  be cast back to a B. Not all instances of A can
  be cast to Bjust those that are actually
  instances of B. If you access class B as a B
  type, you get both the class A and class B data
  and behaviors. The ability for an object to
  represent more than one type is called
  polymorphism.

4
Multiple Inheritance

• Multiple (Implementation) Inheritance is not
  supported in C.
• Multiple Interface Inheritance is supported and
  can replace Multiple implementation inheritance
  in most cases.

5
Dynamic Binding

• C 4.0 introduces a new static type
  called dynamic. When you have an object of
  type dynamic you can do things to it that are
  resolved only at runtime
• dynamic d  GetDynamicObject(...)
• d.M(7)
• The C compiler allows you to call a method with
  any name and any arguments on d because it is of
  type dynamic. At runtime the actual object
  that d refers to will be examined to determine
  what it means to call M with an int on it.
• The type dynamic can be thought of as a special
  version of the type object, which signals that
  the object can be used dynamically. It is easy to
  opt in or out of dynamic behavior any object can
  be implicitly converted to dynamic. Conversely,
  expressions of type dynamic can be implicitly
  converted to object, or indeed any other type, as
  long as there exists a conversion at run time
• dynamic d  7 // compile-time implicit conversion
  
• int i  d     // runtime implicit conversion
• Classes use the virtual keyword for base and
  override for derived classes.

6
Design Issues for OO

• C is Statically type-checked unless otherwise
  defined (using the dynamic keyword).
• dynamic local Local variable // a dynamic
  local variable
• Polymorphism
• public class BaseClass
• public virtual void DoWork()
• public class DerivedClass BaseClass
• public override void DoWork()
• Allocation/Deallocation
• C employs automatic memory management, which
  frees developers from manually allocating and
  freeing the memory occupied by objects. Automatic
  memory management policies are implemented by a
  garbage collector.

7
Summary

• General Characteristics
• C includes both classes and structs.
• Inheritance
• The following is C syntax for defining classes
• public class NewClass ParentClass
• Nested Classes
• C supports static nested classes that are
  directly nested in a class.
• Evaluation
• Since C is based on its predecessors (C
  Java), from which designers learnt and improved,
  it is expected that some of the problems are
  remedied.