From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2008-08-30T10:55:54+09:00
Subject: Re: Access to method in superclass

On Aug 28, 3:15 pm, David Colque <d_col...@yahoo.es> wrote:
> Hi RichardOnRails, thank you very much
> Recently I'm learning this language
>
> Ok
> Version is
> ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
> Operating System is Windows 2003 server (english)
>
> The aim is to bring the code in this java to ruby exactly like this for
> learning purposes.
>
> // The code was drawn from the book "Head First Object Oriented Analysis
> and Design"
> import java.util.*;
> class Airplane {
>   private int speed;
>
>   public Airplane() {
>   }
>
>   public void setSpeed(int speed) {
>     this.speed = speed;
>   }
>   public int getSpeed() {
>     return speed;
>   }
>
> }
>
> class Jet extends Airplane {
>   private static final int MULTIPLIER = 2;
>   public Jet() {
>     super();
>   }
>
>   public void setSpeed(int speed) {
>     super.setSpeed(speed * MULTIPLIER);
>   }
>
>         // HERE STAY MY PROBLEM!!!!!!!!!
>         public void accelerate() {
>     // Access to method "setSpeed" of class Airplane
>     super.setSpeed(getSpeed() * 2);
>   }}
>
> class FlyTest {
>   public static void main(String[] args) {
>     Airplane biplane = new Airplane();
>     biplane.setSpeed(212);
>     System.out.println(biplane.getSpeed());
>     Jet boeing = new Jet();
>     boeing.setSpeed(422);
>     System.out.println(boeing.getSpeed());
>     int x = 0;
>     while (x<4) {
>       boeing.accelerate();
>       System.out.println(boeing.getSpeed());
>       if (boeing.getSpeed()>5000) {
>         biplane.setSpeed(biplane.getSpeed() * 2);
>       } else {
>         boeing.accelerate();
>       }
>       x++;
>     }
>     System.out.println(biplane.getSpeed());
>   }
>
> }
>
> The output is expected is:
> 212
> 844
> 1688
> 6752
> 13504
> 27008
> 1696
>
> --
> Posted viahttp://www.ruby-forum.com/.

Hi David,

OK.  I understand your problem.  You did the natural thing:  you
worked hard to convert the Java program directly into a Ruby program.
It was natural,  but it was the wrong approach.  Nowadays, the
emphasis in programming is Agile Programming and Test-Driven or
Behavior-Driven Programming.  That focuses on writing code in small
pieces and making sure they work correctly.  Then add more code, and
make sure that’s right.

So the approach I recommend is:

•	Make sure the Java code works as advertised. Check out “Test
FlyTest.java” at  http://www.pastie.org/pastes/262610
•	Then I show you how to take the first step in “FlyTest1.rb” at
http://www.pastie.org/pastes/262618
•	Ditto for the second step in “FlyTest2.rb” at  http://www.pastie.org/pastes/262622
•	Ditto for the third step in “FlyTest3.rb” at http://www.pastie.org/pastes/262624

In each of the Ruby code I include the Java code in a couple of
comments.  I do that for convenience as I try to replicate the Java
functionality in Ruby code. If you don’t like that, you could just as
easily keep the Java code open in a separate window.

As you add code try to make it good Ruby code,  nor “Rubyized” Java.
If you don’t know how to express something in Ruby,  look at the code
I originally sketched out for you or post a narrow question on the
newsgroup.  I recommend you do that rather than posting a lot of code.

For more guidance, check out “Agile Ruby”, “Test-Drive Development
(TDD)” and “Behavior-Driven Development (BDD)” in Google.  That’ll
give you some more guidance.

Good luck.

HTH,
Richard