Object Oriented Programming in Matlab

1
Object Oriented Programming in Matlab
Learning Objectives Were now going to introduce
you to some advanced computing concepts, and
well illustrate a simple application that
creates a new data type called an ASSET with
subtypes.
Topics

• Intro to Object-Oriented Programming (OOP)
• An example that creates a ASSET class and shows
  how it might be used
• Extend the ASSET class to subclasses of STOCKS,
  BONDS and SAVINGS.

2
Object-Oriented Programming

• Object-oriented programming has become a focus of
  computer science in recent years
• Simula67, SmallTalk, Objective C, C and Java
  are OOP languages
• OOP is a key part of the first CS courses
• OOP keeps you from getting into certain kinds of
  treacherous problems and tends to foster more
  reliable coding practices
• stimulates a modular coding approach
• allows you to hide details from inadvertent
  alterations
• lets you create a hierarchical code structure
• But often leads to complex and confusing class
  libraries

3
What is OOP

• OOP is part of an on-going effort to add more
  discipline and organization to programming
• it is incorporated to varying degrees in a number
  of languages
• Matlab incorporates OOP
• While the basic OOP concept is simple, the
  practical execution can often seem lost in many
  details!
• The 4 fundamental OOP characteristics
• Abstraction refine away unimportant details and
  describe an object by only the data that is
  important to the task at hand.
• Encapsulation operations must be tightly
  associated with the data on which they can
  operate
• Inheritance a hierarchical structure can be
  effectively employed to describe data and the
  operations on it
• Polymorphism using the same name to refer to
  similar methods to handle different kinds of data

4
Matlab and OOP

• Matlab makes extensive use of OOP at all levels
  of its design and construction
• much of the basic user programming touches on
  parts of this but most is well-hidden (to retain
  the original power of the language)
• but it is accessible to programmers when needed
• see Chapter 33 in MM7 and MatlabgtProgramminggtClass
  es Objects in online help docs
• Were going to go over only the very basics of
  OOP in Matlab
• you can pursue more details on your own (in
  Matlab or Java)
• well illustrate OOP concepts by examining how
  Matlabs Handle Graphics can be used to extend
  its plotting and visualization capabilities.

5
What is an Object?

• Objects (physical or not) have properties and
  behaviors
• Car Properties color, speed, fuel
  consumption, HP Behaviors start, stop,
  turning
• Triangle Properties area, perimeter,
  linestyle, location Behaviors translate,
  rotate, shrink, flip
• Date Properties year, month, day Behaviors
  SetDate, getMonth, isGreater
• Employee Properties SSN, age, gender,
  Behaviors setName, getLastname, calcPay
• Properties information about the object
• Behaviors methods to set, get and process
  properties

6
What is an Object - contd

• OOP lets us create
• a data type
• along with the set of operations that can be
  performed on this data type
• this helps us avoid using wrong operations on
  given data and getting meaningless results
• A Class
• description of the structure of the new data type
  (called fields)
• the set of operations (called methods or
  functions) defined for this data type
• An Object
• a variable having a specific class
• Matlab has certain built-in classes
• but you can easily define your own

7
Examples

• Sometimes the differences between classes and
  objects gets confusing
• Example 1
• House plans the architectural drawings that
  describe how a house is to be constructed are a
  House Class
• A house the house built from the plans is an
  Object or an Instance of the House Class the
  process of building the house is called
  Instantiation of the class. Note that by
  changing some of the dimensions (fields or
  properties), one can create a new house object
  from the same class (plans).
• Example 2
• Flowchart provides the plans for a program (the
  Class)
• Program written from the flowchart is an
  instance of the class (an object)

8
Matlabs Built-in Classes

• Matlabs built-in classes
• others in additional Toolboxes
• You can define your own Matlab classes
• data structure (the fields) is a Matlab struct
• methods (functions) are stored in special
  directory (_at_classname) that is a subdirectory of
  a directory in the Matlab path
• a constructor is a method that is used to create
  an object (an instance of a class)

ARRAY
char
NUMERIC
java class
cell
function handle
structure
user class
int8, uint8, int16, uint16, int32, uint32
single
double
sparse
9
Summary

• OOP will let us create an entirely new data types
  in Matlab
• this is done by creating a class to define this
  data type
• we must also create all the methods (functions)
  that can be used with this special data type
• the internal details are hidden inside the class
• What could we do with this new class?
• some engineering functions require use of special
  data sets and associated methods this is a good
  application and you will find this in some of the
  toolboxes
• we can define subclasses to create a data
  hierarchy
• well look further into this in the next lecture
• Well also look closely at operator overloading,
  especially for Matlabs basic classes

10
Summary

• Learning Objectives
• OOP concepts
• Summary

• Action Items
• Review the lecture
• Consult the reference material
• Consider how this might be extended to other
  applications