OOP Class11

Duck Study

Private instance data members - accessors

Microsoft has stared calling private variables with accessors Properties

Private class memebers the use get and set keyword to set and retrieve data. Get and set are known as accessor methods private members are helpful when you want to also do other things when a data member is changed or change the rutern value under certain conditions. C# Programmer's Reference - Accessors http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vclrfaccessorspg.asp. Lastly accessor also make read only and write only variables possible

<csharp>//private string color read/write private string color;

public string Color {

 get
 {
  return color;
 }
 set
 {
  color = value;
 }

}

//private string color read only private string color;

public string Color {

 get
 {
  return color;
 }

}</syntaxhighlight>

Another property that is a good candidate for a private instance data member is the dogs age

<csharp> private string age;

public int Age {

 //age can only be accessed with get there is no set accessor
 //age must be set with HappyBirthday()
 get
 {
  return age;
 }

}

public int HappyBirthday() {

 age++;
 return age;

}

</syntaxhighlight>

Interfaces

IFlyable <csharp> interface IFlyable

   {
       int CurrentAltitude { get; set; }
       void FlyUP();
       void FlyDown();
       
   }

</syntaxhighlight> Implementation <csharp> class Helicopter : IFlyable

   {

       protected int currentAltitude;

       public Helicopter()
       {
           this.CurrentAltitude = 0;
       }

       public int CurrentAltitude
       {
           get
           {
               return currentAltitude;
           }
           set
           {
               currentAltitude = value;
           }
       }

       public void FlyUP()
       {
           this.CurrentAltitude++;
       }

       public void FlyDown()
       {
           this.CurrentAltitude--;
       }
   }

</syntaxhighlight>

Problems with inheritance

The super class Duck has a swim method.

Duck.swim()

Any class that subclasses the duck class will inherit the swim() method. So far so good all ducks swim

The super class also has a fly() method sa all classes that inherit from duck will get the fly() method.

All ducks don't fly...

Controls is an example of good inhertance

http://iam.colum.edu/oop/classsource/class11/controls.aspx

see

 Hierarchy

Object ---> Control---> WebControl---> BaseDataBoundControl ---> DataBoundControl --->ListControl ---> DropDownList

Strategy Pattern

http://www.dofactory.com/Patterns/PatternStrategy.aspx

Strategy Pattern

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

Ducks From Book

http://iam.colum.edu/oop/browser/browser.aspx?f=/classsource/class11/Duck

http://www.dofactory.com/Patterns/PatternStrategy.aspx

Pretty good example of the strategey method in action.

Characters

Phones

http://iam.colum.edu/oop/classsource/class12/ConsoleApplicationPhoneNoInterface.zip

Review Homework

Problems

Phone interface

Look as phone project. Discuss polymorphic phones interchangeability. Look for possible interfaces to extract.

Homework

Extract interfaces for phone class. Make a web interface for the phone classes.

You should be able to choose an phone type and then dial it and send messages if it is ITxtable.

http://iam.colum.edu/oop/classsource/class12/ConsoleApplicationPhoneNoInterface.zip