Chapter 2 Objects and Classes

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Chapter 2Objects and Classes

• Bernard Chen
• Spring 2006

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2.1 What is OO programming?

• Object an atomic unit that has structure and
  state
• Information hiding Black-box analogy
• Encapsulation grouping of data and functions
• Inheritance mechanism allows extending
  functionality of an object.

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How does C support OO

• Template the logic is independent of
• the type
• Inheritance
• Polymorphism allows us to implement
• new types (classes) that
  
• share same logic

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2.2 Basic Class Syntax

• Class members either data or functions and
  categorized into either public, protected,or
  private.
• Public visible to an instance of (object) a
  class
• Private visible only inside an instance of a
  class
• Protected similar to private but visible to
  derived classes.
• Default all members are private

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Constructors

• Member functions that describe how an object is
  declared and initialized.
• If no constructor defined, compilers will
  generate one called default constructor.
• Explicit constructors prevent automatic type
  conversion.

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Constant Member Function

• Constant functions (accessors) functions that
  do not change any data member.
• const is a part of the function signature.
  const return_type name(const parameter_list)
  const
• Interface describes what can be done to the
  object, i.e. the header.
• Implementation represents internal processes
  specified by the interface.

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Big three Destructor, Copy Constructor, and
Operator

• Destructor tells how an object is destroyed and
  freesdresources when it exists scope.
• IntCell()
• Copy Constructor allows a new object construct
  using the data in an existing one.
• IntCella(5) // a new IntCellcall a
• IntCellb(a) // another IntCellcall b
• Operator copy assignment, copies data members
  using by default.gt may cause shallow copying.

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This (predefine pointer)
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2.3 Additional C Features

• Operator overloading extending the types to
  which an operator can be applied.
• example string xMarys score is
• int y95
• string zxy
• ., ., ?, sizeof cant be overloaded

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Additional C Features

• Type conversion creates a temporary object of a
  new type
• Example int a 5
• double b a //implicit cast

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2.5 Exceptions (report error)

• An object that stores information transmitted
  outside the normal return sequence and is used to
  signal exceptional occurrences
• Handle exceptions by throw and catch clauses.

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Exceptions example

• try
• for (intn0 nlt10 n)
• if (ngt9) throw "Out of range"
• catch (char str)
• coutltlt "Exception " ltlt strltlt endl

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2.6 String Class

• C string array of character terminated by \0
• C standard string a STL class with all
  overload operators and built-in functions
• http//www.bgsu.edu/departments/compsci/docs/strin
  g.html

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Summary

• Construction/ destruction of objects
• Copy semantics
• Overloading
• Implicit/explicit type conversion
• Information hiding/atomicity