DCO10105 Object-Oriented Programming and Design

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DCO10105 Object-Oriented Programming and Design

• Lecture 6 More on class construction
  UML and an introduction to inheritance
• More on class construction
• Multiple inclusion
• Use of accessor and mutator
• Function overload and signature
• Members of pointer
• The resolution operator and namespace
• UML and an introduction to inheritance
• UML Class diagram
• Some class diagrams in the real world
• Some class diagrams for typical applications
• -- By Rossella Lau

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Revisit IntArray.h IntArray.cpp

• inndef _INT_ARRAY_Hdefine
  _INT_ARRAY_H......endif
• These are pre-processor statements to avoid
  multiple inclusion
• The pre-processor uses a symbol _INT_ARRAY_H to
  indicate that the body within inndef -- endif,
  including _INT_ARRAY_H, will be defined if it is
  not defined yet
• When the same header file is included the second
  time, since it is already defined, the body will
  not be included

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The dynamic array -- pointer

• The dynamic array array actually is a pointer
• Its main purpose is to get dynamic memory
  allocation for the array
• However, whenever you have a pointer variable, it
  complicates the constructors and destructors and
  usually you must define your own rather than
  using those generated by the compiler
• In other words, for simple classes such as
  clockType and Qudratic, we can use the compiler
  generated constructors and destructors

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The identifier starting with _

• Identifiers of data members in IntArray start
  with _ (an underscore)
• Traditionally, C defines system (library
  functions) variables with a prefix _ to avoid
  conflict with programmer defined variable names

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Use of accessor and mutator

• Although a member can access any other members in
  a class, it is a good habit to use accessor and
  mutator in service functions and use mutator to
  set the value for the data in the constructor if
  the respective data does have a domain checking
  and maintaining in the mutator e.g.,
  DateType.cpp
• I.e., Data members are usually only directly
  referenced in constructors, accessors, and
  mutators recheck IntArray.cpp Quadratic.cpp

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Function overload

• Several constructor ids and identical function
  ids can exist in the same class or the same
  program
• IntArray(int), IntArray(IntArray const )
• fillData(double,size_t), fillData(int,size_t)
• Same function ids with different signatures are
  allowed in modern languages
• Return type parameters of a function are the
  functions signature
• When a function call is encountered, the compiler
  checks the type(s) of its parameter(s), the
  signature, and finds the function with such
  signature to call

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and namespace

• identifies a member of a class (. identifies a
  member of an object)
• can also identify members in namespace
• Namespace Maliks slide 818-23
• ?Same symbol but different application
• You cannot use using namespace IntArray to save
  the typing of IntArray for the function
  implementation in IntArray.cpp

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UML

• Unified Modeling Language
• Software blueprint language
• Similar to blueprints, standard graphical
  language, for the architects and builders
• There are nine kinds of modeling diagrams
• Use Case diagrams, Class diagrams, Object
  diagrams, Sequence diagrams, Collaboration
  diagrams, Statechart diagrams, Activity diagrams,
  Component diagrams, and Deployment diagrams
• Reference www.borland.com

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Class diagram

• It gives an overview of a system by showing the
  relationships among them
• Association relationship between instances of
  two classes
• It is a link in a diagram
• Aggregation an association in which one class
  belongs to a collection
• It is a link with a diamond end pointing to the
  part containing the whole
• Generation indicating inheritance between
  classes
• It is a link with a triangle end pointing to the
  base class from sub classes

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Navigation and multiplicity

• In the above class diagram, it uses navigability
  arrow to represent the relationship rather than
  the standard
• It shows which direction the association can be
  traversed
• Multiplicity shows the possible instances for an
  aggregation e.g.,
• An order has at least one order item
• A catalog has zero or many products

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An example customer orders

• http//bdn.borland.com/article/0,1410,31863,00.htm
  lclassdiagrams

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Class notation

• A 3-piece rectangle E.g., Maliks Figure 12-1

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Visibility and scope

• http//bdn.borland.com/article/images/31863/classd
  iagram.html

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Introduction to inheritance

• A sub class has the attributes and properties
  (operations) of its base class
• A sub class inherits everything from its base
  class in OO view all the data members and
  function members
• It is quite similar to class taxonomy or class
  classification in the real world
• Animals can be classified as mammal, bird, fish
  there are different kinds of mammals man, pet,
  wild animal, farm animal, whale, etc

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Real world example CityU
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Real world example Animal
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Application The shapes
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Application Course management
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A class diagram for gourmetCoffee
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Other typical applications

• A restaurant system
• A retail system
• A course management system
• A library system
• A payroll system

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Summary

• In this class, we revisited class construction
  with some related concepts and techniques
  pre-processors supports, pointer member and
  class, good programming practice in using
  accessor and mutator, and namespace
• The class diagram of the UML helps in modeling a
  system
• The class diagram also introduces the
  relationship of inheritance

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Reference

• Malik 8.3, 12.1.1, 13
• http//bdn.borland.com/article/0,1410,31863,00.htm
  l
• -- END --