# Access to method in superclass **URL:** \ **Category:** Ruby\ **Created:** [August 25, 2008, 8:39pm UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815 "2008-08-25T20:39:18Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 25, 2008, 8:39pm UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/1 "2008-08-25T20:39:18Z")
LIKE ACCEDING TO THE METHOD " setSpeed" OF THE SUPERCLASS “Airplane”. Thak you ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 26, 2008, 2:15am UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/2 "2008-08-26T02:15:25Z")
On Aug 25, 2:35 pm, David C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > LIKE ACCEDING TO THE METHOD " setSpeed" OF THE SUPERCLASS “Airplane”. > Thak you > > Attachments:[http://www.ruby-forum.com/attachment/2606/prueba1.rb](http://www.ruby-forum.com/attachment/2606/prueba1.rb) > > – > Posted viahttp://www.ruby-forum.com/. Hi David, Your access to Airplane::setSpeed is working. On line 55, you create an Airplane::Jet instance with @speed=0 On line 56, you invoke that setSpeed on the instance with argument 422 so the method on line 38 is called with 422 which in turn invokes Airplane::setSpeed with the argument 422\*Multiplier, of 844, which is then set in @speed of the Airplane::Jet instance On line 57, you print out the 844 Then on line 57, you invoke Line 56 set the Jet’s speed to 0 Line 57 with argument 422 set the Jet’s speed to 422\*Multiplier, or 844 and printed it Line 60 invoked accelerate, which in turn invoked Line 45 setSpeed(getSpeed()\*2) getSpeed returned your 844, which then got doubled to 1688 which was used as the argument to setSpped, which applied the Multiplier so the speed was set to 3376 Line 61 used getSpeed to retrieve the 3376, which then got printed. All this is confirmed by lines 2 and 2 of your output. HTH, Richard ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 26, 2008, 5:23pm UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/3 "2008-08-26T17:23:52Z")
RichardOnRails wrote: > On Aug 25, 2:35 pm, David C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > LIKE ACCEDING TO THE METHOD " setSpeed" OF THE SUPERCLASS “Airplane”. > > Thak you > > > > Attachments:[http://www.ruby-forum.com/attachment/2606/prueba1.rb](http://www.ruby-forum.com/attachment/2606/prueba1.rb) > > > > – > > Posted viahttp://www.ruby-forum.com/. > > Hi David, > > Your access to Airplane::setSpeed is working. > > On line 55, you create an Airplane::Jet instance with @speed=0 > On line 56, you invoke that setSpeed on the instance with argument 422 > so the method on line 38 is called with 422 > which in turn invokes Airplane::setSpeed with the argument > 422\*Multiplier, of 844, > which is then set in @speed of the Airplane::Jet instance > On line 57, you print out the 844 > > Then on line 57, you invoke > > Line 56 set the Jet’s speed to 0 > Line 57 with argument 422 set the Jet’s speed to 422\*Multiplier, or > 844 and printed it > > Line 60 invoked accelerate, which in turn invoked > Line 45 setSpeed(getSpeed()\*2) > getSpeed returned your 844, which then got doubled to 1688 > which was used as the argument to setSpped, which applied the > Multiplier > so the speed was set to 3376 > Line 61 used getSpeed to retrieve the 3376, which then got printed. > > All this is confirmed by lines 2 and 2 of your output. > > HTH, > Richard class Jet \< Airplane MULTIPLIER = 2 def initialize super end def setSpeed(speed) super(speed\*MULTIPLIER) end def accelerate # TROUBLE!!! # LIKE ACCEDING TO THE METHOD " setSpeed" # OF THE SUPERCLASS “Airplane” Airplane::setSpeed(getSpeed()\*2) end end At the time of making it run it leaves the error > ruby prueba1.rb > prueba1.rb:28:in `accelerate': undefined method `setSpeed’ for > Airplane:Class (NoMethodError) > from prueba1.rb:43:in `principal’ > from prueba1.rb:57 > 212 > 844 > Exit code: 1 ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 28, 2008, 9:20pm UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/4 "2008-08-28T21:20:29Z")
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 ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 28, 2008, 3:15am UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/5 "2008-08-28T03:15:56Z")
On Aug 26, 11:19 am, David C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > Hi David, > > > Multiplier > > def initialize > > end > > 844\>Exit code: 1 > > – > Posted viahttp://www.ruby-forum.com/. Hi David, I can’t see what’s wrong on your program/machine. I ran the code you posted unchanged and got the following output: 212 844 3376 54016 216064 864256 1696 The first question I’d ask is, what version of Ruby/OS are you running … though I doubt that will be too helpful? I’m running: ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32] WinXP-Pro/SP2 The second question is, are you up to cleaning up code and debugging it? At [http://www.pastie.org/261401](http://www.pastie.org/261401), I posted a version of your program that is closer to what I understand to be “The Ruby Way”. I don’t understand your purpose, so I can’t do anymore. I hope this version runs on your machine as it does on mine. I also hope it leads to a clearer understanding of your program flow. The version I posted doesn’t produce the same numbers that your original did, but I don’t want to spend anymore time on it. As I said, my goal is to help you get closer to “The Ruby Way.” Best wishes, Richard ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 28, 2008, 9:32pm UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/6 "2008-08-28T21:32:44Z")
Hello. It’s a gotcha in Ruby - there’s NO WAY to access ancestor’s method setSpeed from your own method accelerate. As you see, the word super itself is a call to ancestor’s method of the same name as the method you are currently in. And there’s no other use of super, so you cannot call ancestor’s (overridden) method of a different name than the method you’re actually in. AFAIK they say that you shouldn’t need to. If you do, you can refactor your code and it will be a good thing to do. TPR. ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 28, 2008, 10:24pm UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/7 "2008-08-28T22:24:26Z")
Thomas B. wrote: > Hello. > > It’s a gotcha in Ruby - there’s NO WAY to access ancestor’s method > setSpeed from your own method accelerate. As you see, the word super > itself is a call to ancestor’s method of the same name as the method you > are currently in. And there’s no other use of super, so you cannot call > ancestor’s (overridden) method of a different name than the method > you’re actually in. > > AFAIK they say that you shouldn’t need to. If you do, you can refactor > your code and it will be a good thing to do. > > TPR. Thank you very much. Then continuous learning … ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [August 30, 2008, 4:04am UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/8 "2008-08-30T04:04:54Z")
On Aug 28, 3:15 pm, David C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ``` > this.speed = speed; > super(); > > ``` > > }} > while (x\<4) { > } > 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](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](http://www.pastie.org/pastes/262618) • Ditto for the second step in “FlyTest2.rb” at [http://www.pastie.org/pastes/262622](http://www.pastie.org/pastes/262622) • Ditto for the third step in “FlyTest3.rb” at [http://www.pastie.org/pastes/262624](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 ---
**Author:** ![crucoba](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/e8c25b/32.png) [@crucoba](https://www.ruby-forum.com/u/crucoba)\ **Post date:** [September 2, 2008, 12:49am UTC](https://www.ruby-forum.com/t/access-to-method-in-superclass/146815/9 "2008-09-02T00:49:37Z")
ok, see you later!!! thk