7:57 a.m.
* 1 Fedora Weekly News Issue 269
o 1.1 Announcements
+ 1.1.1 Fedora Announcement News
# 1.1.1.1 Changes to the Packaging Guidelines
+ 1.1.2 Fedora Development News
# 1.1.2.1 Beta change freeze
# 1.1.2.2 Fedora 15 schedule to slip an additional week
+ 1.1.3 Fedora Events
# 1.1.3.1 Upcoming Events (March - May 2011)
# 1.1.3.2 Past Events
# 1.1.3.3 Additional information
o 1.2 Fedora In the News
+ 1.2.1 Red Hat Proves That Open Source Is Good for Business (PC World)
o 1.3 Ambassadors
+ 1.3.1 Welcome New Ambassadors
+ 1.3.2 Summary of traffic on Ambassadors mailing list
+ 1.3.3 Summary of events reported on Ambassadors mailing list
+ 1.3.4 Summary of traffic on FAmSCo mailing list
o 1.4 QualityAssurance
+ 1.4.1 Test Days
+ 1.4.2 Anaconda testing
+ 1.4.3 GNOME Tweak Tool testing
+ 1.4.4 Fedora 15 Beta preparation
+ 1.4.5 Improving pre-release download page
o 1.5 Security Advisories
+ 1.5.1 Fedora 15 Security Advisories
+ 1.5.2 Fedora 14 Security Advisories
+ 1.5.3 Fedora 13 Security Advisories
o 1.6 LATAM Fedora!
+ 1.6.1 Ruby Capítulo 2 : Una clase algo más completa
# 1.6.1.1 Constantes vs variables
# 1.6.1.2 El poder de herencia
# 1.6.1.3 Espacios de nombres
# 1.6.1.4 Herencia múltiples vs Mixins
* 1.6.1.4.1 mixin_module.rb
- Fedora Weekly News Issue 269 -
Welcome to Fedora Weekly News Issue 269[1] for the week ending March 30, 2011. What
follows are some highlights from this issue.
This issue begins with announcements from the Fedora Project, including changes to the
packaging guidelines and an additional week slip of the Fedora 15 release date. One
article for Fedora In the News this week from PC World on Red Hat's financial success.
In Ambassador news, details on new members of the team, a summary of discussion on the
Ambassador and FAmSCo lists, and a couple event reports. In Quality Assurance news,
details on the latest and upcoming Test Days on power management, printing and ABRT, as
well as various reports leading up to the Fedora 15 beta release. Security Advisories
brings us current with the security-related package releases this past week for Fedora 13,
14 and 15, and in our Latin American beat this week, a second installment of Guillermo
Gomez's Ruby Primer, in Spanish. Enjoy!
An audio version of some issues of FWN - FAWN - are available! You can listen to existing
issues[2] on the Internet Archive. If anyone is interested in helping spread the load of
FAWN production, please contact us!
If you are interested in contributing to Fedora Weekly News, please see our 'join'
page[3]. We welcome reader feedback: news(a)lists.fedoraproject.org
FWN Editorial Team: Pascal Calarco, Adam Williamson
1. ↑ http://fedoraproject.org/wiki/FWN/Issue269
2. ↑ http://www.archive.org/search.php?query=subject%3A%22FWN%22
3. ↑ http://fedoraproject.org/wiki/NewsProject/Join
-- Announcements --
In this section, we cover announcements from the Fedora Project, including general
announcements[1], development announcements[2] and Events[3].
Contributing Writer: Pascal Calarco
1. ↑ http://lists.fedoraproject.org/pipermail/announce/
2. ↑ http://lists.fedoraproject.org/pipermail/devel-announce/
3. ↑ http://fedoraproject.org/wiki/Events
--- Fedora Announcement News ---
The announcement list is always exclusive for the Fedora Community. Please, visit the past
announcements at[1]
1. ↑ https://admin.fedoraproject.org/mailman/listinfo/announce
---- Changes to the Packaging Guidelines ----
Tom 'Spot' Callaway announced[1],
"Here are the changes to the Fedora Packaging Guidelines for this week:
The Packaging:PHP guidelines have been updated to reflect that PEAR documentation provided
by upstream are installed in %{pear_docdir}, should stay there, and must be marked as
%doc.
Additionally, the definition of pear_docdir has been defined as %{_docdir}/pear.
https://fedoraproject.org/wiki/Packaging:PHP
---
The Java guidelines have been updated to add information and sample template for Maven 3
(Fedora 15+).
https://fedoraproject.org/wiki/Packaging:Java
---
These guidelines (and changes) were approved by the Fedora Packaging Committee (FPC).
Many thanks to Remi Collet, Stanislav Ochotnicky, and all of the members of the FPC, for
assisting in drafting, refining, and passing these guidelines.
As a reminder: The Fedora Packaging Guidelines are living documents! If you find something
missing, incorrect, or in need of revision, you can suggest a draft change. The procedure
for this is documented here [2]
Thanks,
~spot"
1. ↑ http://lists.fedoraproject.org/pipermail/announce/2011-March/002942.html
2. ↑ http://fedoraproject.org/wiki/Packaging/Committee#GuidelineChangeProcedure
--- Fedora Development News ---
The Development Announcement[1] list is intended to be a LOW TRAFFIC announce-only list
for Fedora development.
Acceptable Types of Announcements
* Policy or process changes that affect developers.
* Infrastructure changes that affect developers.
* Tools changes that affect developers.
* Schedule changes
* Freeze reminders
Unacceptable Types of Announcements
* Periodic automated reports (violates the INFREQUENT rule)
* Discussion
* Anything else not mentioned above
1. ↑ https://admin.fedoraproject.org/mailman/listinfo/devel-announce
---- Beta change freeze ----
Dennis Gilmore announced[1],
"Hi All a heads up that change freeze for the Fedora 15 Beta is Tuesday April 5th.
After this point only accepted blocker bugs will be pulled in. Please limit your changes
to try and avoid unintended breakages.
thanks
Dennis"
1. ↑ http://lists.fedoraproject.org/pipermail/devel-announce/2011-March/000773...
---- Fedora 15 schedule to slip an additional week ----
Jared K. Smith announced[1]
"The Fedora 15 development cycle is well under way, and making good progress.
Yesterday I met[1] with Release Engineering, QA, the Fedora Program Manager, and we
decided that in order to accommodate some late-breaking changes, we're going to need
to slip the Fedora 15 release schedule by a week in order to have adequate time to do
proper testing of the candidate images before the Beta. This slip will affect the entire
Fedora 15 development cycle, as shown in the chart below:
o F15 Devel Start 2010-11-02
o Feature Submission Deadline 2011-01-25
o Feature Freeze 2011-02-08
o Branch From Rawhide 2011-02-08
o Software String Freeze 2011-02-15
o Alpha Change Deadline 2011-02-15
o Alpha Release 2011-03-08
N O W -----------------------
o Software Translation Deadline 2011-04-05
o Beta Change Deadline 2011-04-05
o Features 100% Complete 2011-04-05
o Beta Release 2011-04-19
o Final Change Deadline 2011-05-09
o Compose RC 2011-05-10
o GA 2011-05-24
Robyn Bergeron has also kindly updated the complete break-out of the Fedora release
schedule, which is available[2]. If you have any questions or concerns, please don't
hesitate to let me know.
-- Jared Smith Fedora Project Leader "
1. ↑ http://lists.fedoraproject.org/pipermail/devel-announce/2011-March/000772...
2. ↑ http://rbergero.fedorapeople.org/schedules/f-15/
--- Fedora Events ---
The purpose of event is to build a global Fedora events calendar, and to identify
responsible Ambassadors for each event. The event page is laid out by quarter and by
region. Please maintain the layout, as it is crucial for budget planning. Events can be
added to this page whether or not they have an Ambassador owner. Events without an owner
are not eligible for funding, but being listed allows any Ambassador to take ownership of
the event and make it eligible for funding. In plain words, Fedora events are the
exclusive and source of marketing, learning and meeting all the fellow community people
around you. So, please mark your agenda with the following events to consider attending or
volunteering near you!
---- Upcoming Events (March - May 2011) ----
* North America (NA)[1]
* Central & South America (LATAM): [2]
* Europe, Middle East, and Africa (EMEA)[3]
* India, Asia, Australia (India/APJ)[4]
1. ↑ http://fedoraproject.org/wiki/Events#FY12_Q1_.28March_2011_-_May_2011.29
2. ↑ http://fedoraproject.org/wiki/Events#FY12_Q1_.28March_2011_-_May_2011.29_2
3. ↑ http://fedoraproject.org/wiki/Events#FY12_Q1_.28March_2011_-_May_2011.29_3
4. ↑ http://fedoraproject.org/wiki/Events#FY12_Q1_.28March_2011_-_May_2011.29_4
---- Past Events ----
Archive of Past Fedora Events[1]
1. ↑ http://fedoraproject.org/wiki/FedoraEvents/PastEvents
---- Additional information ----
* Reimbursements -- reimbursement guidelines.
* Budget -- budget for the current quarter (as distributed by FAMSCo).
* Sponsorship -- how decisions are made to subsidize travel by community members.
* Organization -- event organization, budget information, and regional
responsibility.
* Event reports -- guidelines and suggestions.
* LinuxEvents -- a collection of calendars of Linux events.
-- Fedora In the News --
In this section, we cover news from the trade press and elsewhere that is re-posted to the
Fedora Marketing list[1].
http://fedoraproject.org/wiki/Marketing
Contributing Writer: Pascal Calarco
1. ↑ http://lists.fedoraproject.org/pipermail/marketing/
--- Red Hat Proves That Open Source Is Good for Business (PC World) ---
Rahul Sundaram forwarded[1] a posting on Red Hat's financial success:
"Critics of free and open source software are fond of making the argument that
software must be locked up, patented and jealously guarded if it is to serve as the basis
for a successful business. Well, Red Hat just refuted such claims in a big way this week
with its fourth quarter earnings report, which blew away analysts' expectations and
placed the company well on track for billion-dollar revenues in the upcoming year."
Based in North Carolina, Red Hat is the company behind both the Fedora and the Red Hat
Enterprise Linux (RHEL) Linux distributions. Fedora is the free, community version of the
software, while RHEL is sold as acommercial product with support and services."
The full article is available[2].
1. ↑ http://lists.fedoraproject.org/pipermail/marketing/2011-March/013758.html
2. ↑
http://www.pcworld.com/businesscenter/article/223346/red_hat_proves_that_...
-- Ambassadors --
This section covers the news surrounding the Fedora Ambassadors Project[1].
Contributing Writer: Sankarshan Mukhopadhyay
1. ↑ http://fedoraproject.org/wiki/Ambassadors
--- Welcome New Ambassadors ---
This week the Fedora Ambassadors Project had a couple of new members joining.
Everton Cardoso from Brazil mentored by Daniel Bruno
--- Summary of traffic on Ambassadors mailing list ---
Christoph Wickert raised [1] some questions regarding the budget [2] Max Spevack provided
[3] actual figures from the expenses. David Nalley mentioned [4] that some of the issues
raised in the mail were also part of the Board IRC meeting and, discussions were ongoing
as the same was an agenda item in the upcoming Board meeting.
Onyeibo Oku asked [5] if there was an existing print-ready, A5 sized booklet covering the
basics of Fedora for handing out at events. Zoltan Hopper responded [6] about a scratch
document available at the Marketing Page. There was further discussion around the
difference between a Quick-Start and a Handbook [7] and the possibility of building a
Quick Start Guide [8] based upon the SXSW Materials [9]
Christoph Wickert posted [10] Minutes of EMEA Ambassadors Meeting [11] The thread [12] had
additional discussion around allocation of funds under budget line items and, expense
planning based on projected needs. The decision making process within FAmSCo was also
discussed.
David Ramsey posted [13] meeting notes [14] from the APAC Ambassadors meeting on
2011-03-19
David Ramsey informed [15] about an upcoming Power Management Test Day [16] and
subsequently posted [17] about the Printing and ABRT Retrace Server Test Days
Máirín Duffy asked [18] if there was a group photograph from a recent event with the aim
of updating the FUDCon Zurich group phot that is on fedoraproject.org page
Christoph Wickert posted [19] a 'Last Call for Orders" for F14 media for any
event at EMEA and added a link to the Inventory [20] for helping to search for the nearest
anchor point
Pierros Papadeas posted [21] Meeting Minutes for FAmSCo meeting of 2011-03-26
Buddhika Kurera requested help [22] in finding a co-speaker for CLT2011
Paul Mellors posted [23] about an idea for a documentary [24] similar to "Revolution
OS"
Adam Miller put out a last call for funding for Texas Linux Fest 2011 [25]
1. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017242.html
2. ↑ https://fedoraproject.org/wiki/FAmSCo_report_2011-02
3. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017245.html
4. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017317.html
5. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017252.html
6. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017253.html
7. ↑ http://fedoraproject.org/wiki/User:Sankarshan/FedoraHandbook
8. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017261.html
9. ↑ https://fedoraproject.org/wiki/Design/SXSW_Materials
10. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017264.html
11. ↑
http://meetbot.fedoraproject.org/fedora-meeting/2011-03-23/emea_ambassado...
12. ↑
http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/thread.ht...
13. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017265.html
14. ↑
http://meetbot.fedoraproject.org/fedora-meeting/2011-03-19/apac.2011-03-1...
15. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017267.html
16. ↑ https://fedoraproject.org/wiki/Test_Day:2011-03-24
17. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017312.html
18. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017282.html
19. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017293.html
20. ↑ https://fedorahosted.org/emea-swag-tracking/wiki/Inventory
21. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017296.html
22. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017299.html
23. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017314.html
24. ↑ https://fedoraproject.org/wiki/Fedora_Documentary
25. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017310.html
--- Summary of events reported on Ambassadors mailing list ---
Christoph Wickert reported [1] on the Chemnitzer Linuxtage event with more details about
undertaking similar tasks using different distributions.
Fabian Affolter summarized [2] all the CLT2011 reports
1. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017241.html
2. ↑ http://lists.fedoraproject.org/pipermail/ambassadors/2011-March/017284.html
--- Summary of traffic on FAmSCo mailing list ---
Pierros Papadeas posted [1] the Agenda for the FAmSCo meeting of 2011-03-26 [2]
Joerg Simon, as the Fedora Ambassador Membership Administrator, informed FAmSCo [3] about
existing continuous violations of Fedora Ambassador Conduct [4] Follow-up discussions
happened on the ticket and the thread [5]
1. ↑ http://lists.fedoraproject.org/pipermail/famsco/2011-March/000736.html
2. ↑ https://fedoraproject.org/wiki/FAmSCo_agenda#2011-3-26_agenda
3. ↑ http://lists.fedoraproject.org/pipermail/famsco/2011-March/000737.html
4. ↑ https://fedorahosted.org/famsco/ticket/156
5. ↑ http://lists.fedoraproject.org/pipermail/famsco/2011-March/thread.html#737
-- QualityAssurance
In this section, we cover the activities of the QA team[1]. For more information on the
work of the QA team and how you can get involved, see the Joining page[2].
Contributing Writer: Adam Williamson
1. ↑ http://fedoraproject.org/wiki/QA
2. ↑ http://fedoraproject.org/wiki/QA/Join
--- Test Days ---
Thursday 2011-03-24 was power management Test Day[1]. The event produced a great turnout
of testers who provided results on a wide range of hardware, and the developers are
already looking at the bugs filed. Thanks to everyone who came out to help.
This Tuesday, 2011-03-29, was printing Test Day[2]. The turnout was a little smaller than
we hoped, but the testers who did come managed to find lots of bugs, and Fedora's
printing maintainer, Tim Waugh, was very happy with all the results.
This Thursday, 2011-03-31, will be ABRT Test Day[3]. As well as checking that ABRT
(Fedora's automated crash report tool) is working as expected for Fedora 15, we'll
be testing out a big new feature, the retrace server[4]. This allows you to submit crash
reports to a remote server which will generate the backtrace - avoiding the need for you
to download and install often large debuginfo packages in order to submit reports. Please
come along and help us test this exciting new feature!
There is currently no Test Day planned for next Thursday, 2011-04-07. Take the day off!
1. ↑ http://fedoraproject.org/wiki/Test_Day:2011-03-24
2. ↑ http://fedoraproject.org/wiki/Test_Day:2011-03-29
3. ↑ http://fedoraproject.org/wiki/Test_Day:2011-03-31_ABRT_Retrace_Server
4. ↑ http://fedoraproject.org/wiki/Features/RetraceServer
--- Anaconda testing ---
James Laska requested testing of an installer image which included updated versions of
anaconda and lorax that needed testing before being approved as stable updates[1]. Several
testers responded, and the updates were soon approved.
1. ↑ http://lists.fedoraproject.org/pipermail/test/2011-March/098018.html
--- GNOME Tweak Tool testing ---
Michel Salim announced that GNOME Tweak Tool, an application for tweaking various advanced
settings in GNOME 3, was now available for testing[1]. Several group members thanked
Michel for the announcement and provided feedback on the tool.
1. ↑ http://lists.fedoraproject.org/pipermail/test/2011-March/098107.html
--- Fedora 15 Beta preparation ---
The third Beta blocker/nice-to-have review meeting took place on 2011-03-25[1], and the
team worked through the full list of proposed Beta blocker and nice-to-have bugs. The
first test compose was scheduled for Tuesday 2011-03-22, but could not be completed on
that day due to various outstanding bugs and the lack of the planned NetworkManager 0.9
packages. At a special release schedule meeting on Wednesday 2011-03-23[2], the QA and
release engineering teams, and the Fedora Project Leader, agreed that the late arrival of
NetworkManager 0.9 justified a one week slip in the release schedule. The first test
compose was then set for Tuesday 2011-03-29.
1. ↑
http://meetbot.fedoraproject.org/fedora-bugzappers/2011-03-25/f-15-beta-b...
2. ↑
http://meetbot.fedoraproject.org/fedora-meeting/2011-03-23/fedora-meeting...
--- Improving pre-release download page ---
Tim Flink passed on some feedback[1] he had received from a new tester who had downloaded
a pre-release and asked some questions in the #fedora IRC channel, which does not handle
pre-release issues. He suggested that it would be a good idea to add some text to the
pre-release download page[2] explaining the right places to go to post feedback and get
help with pre-release issues. Jóhann Guemundsson and Adam Williamson both suggested filing
a request with the websites team, and Tim reported[3] that he had filed a ticket[4].
1. ↑ http://lists.fedoraproject.org/pipermail/test/2011-March/098160.html
2. ↑ http://fedoraproject.org/get-prerelease
3. ↑ http://lists.fedoraproject.org/pipermail/test/2011-March/098173.html
4. ↑ http://fedorahosted.org/fedora-websites/ticket/45
-- Security Advisories --
In this section, we cover Security Advisories from fedora-package-announce from the past
week.
http://lists.fedoraproject.org/pipermail/package-announce
Contributing Writer: Pascal Calarco
--- Fedora 15 Security Advisories ---
* libxml2-2.7.8-6.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0570...
* logrotate-3.7.9-8.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0569...
* asterisk-1.8.3.2-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0569...
* php-doctrine-Doctrine-1.2.4-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0569...
* roundcubemail-0.5.1-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0569...
* nss-3.12.9-14.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0568...
* subversion-1.6.16-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0567...
* libcgroup-0.37.1-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0567...
* phpMyAdmin-3.3.10-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0567...
* maniadrive-1.2-29.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0566...
* php-eaccelerator-0.9.6.1-6.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0566...
* php-5.3.6-1.fc15 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0566...
--- Fedora 14 Security Advisories ---
* phpMyAdmin-3.3.10-1.fc14 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0570...
* wordpress-3.1-1.fc14 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0570...
* gnash-0.8.9-1.fc14 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0567...
* libcgroup-0.36.2-6.fc14 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0566...
* krb5-1.8.2-9.fc14 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0565...
--- Fedora 13 Security Advisories ---
* phpMyAdmin-3.3.10-1.fc13 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0570...
* wordpress-3.1-1.fc13 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0569...
* gnash-0.8.9-1.fc13 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0567...
* krb5-1.7.1-18.fc13 -
http://lists.fedoraproject.org/pipermail/package-announce/2011-March/0565...
-- LATAM Fedora! --
LATAM Fedora is a regular column of Spanish language contributions around open source
software. It is our first expansion into incorporating foreign language content into
FWN.
This week's contribution is from Guillermo Gómez, a second installment primer on Ruby.
Enjoy!
---- Ruby Capítulo 2 : Una clase algo más completa ----
Siguiendo nuestra secuencia al estilo tutorial, en esta edición vamos a completar un poco
más nuestras clases, introduciresmo los conceptos de métodos y variables de clase.
Una variable de clase es una variable compartida de la clase misma. Sólo existe una copia
de una variable de clase en particular para una clase dada. Los nombres de las variables
de clase comienzan con @@ tal como en @@reproducciones.
1 class Cancion
2 @@reproducciones = 0
3
4 def Cancion.reproducciones
5 @@reproducciones
6 end
7
8 def reproducir
9 @@reproducciones =+ 1
10 end
11 end
A diferencia de las variables de instancia y variables globales, las variables de clase
deben se inicializadas antes de poder ser utilizadas, usualmente se hace con una
declaración simple en el cuerpo de la definición de la clase. En el código anterior
igualmente se ha introducido el concepto de método de clase. Un método de clase es un
método que no necesita que se instancie la clase para ser invocado, es decir, "son
métodos propios de la clase y no de sus objetos".
Su utilidad es obvia en el ejemplo, se quiere saber cuántas reproducciones se han hecho en
total en nuestro reproductor de música. Esta información no es específica a una canción en
particular, es decir, no es sujeto de las instancias sino de la clase misma. La diferencia
al momento de declarar el método de clase es que debe anteponer el nombre de la clase al
método, tiene dos opciones, o usar explícitamente Cancion, o self. El uso de *self"
da mayor flexibilidad ya que permite cambiar el nombre de la clase sin mayores traumas.
1 class Cancion
2 @@reproducciones = 0
3
4 def self.reproducciones
5 @@reproducciones
6 end
7
8 def reproducir
9 @@reproducciones =+ 1
10 end
11 end
---- Constantes vs variables ----
Las variables y constantes en Ruby mantienen referencias a objetos. Las variables no
poseen un tipo intrínseco, a cambio el tipo es únicamente definido por los mensajes a los
que responde el objeto referenciado.
Una constante en Ruby también es una referencia a un objeto. Las constantes son creadas
cuando son asignadas por primera vez, a diferencia de otros lenguajes Ruby le permite
alterar el valor de las constantes si bien ello provocará un mensaje de alerta. En general
usted no debe alterar una constante en tiempo de ejecución y debería evitarlo a toda
costa.
1 >> MI_CONSTANTE = 1
2 => 1
3 >> MI_CONSTANTE = 2
4 (irb):23: warning: already initialized constant MI_CONSTANTE
5 => 2
Note como las constantes pueden declararse dentro de la definición de clase lo que nos
lleva a la definición de constante de clase y a la noción de espacios de nombres por la
forma en que nos referimos a dichas constantes.
1 class Cancion
2 VERSION="1.0"
3 end
1 >> Cancion::VERSION
2 => "1.0"
3 >> VERSION
4 => "1.8.7"
Note que VERSION no referencia ni colisiona con Cancion::VERSION.
---- El poder de herencia ----
Tal vez el santo grial de la programación es el principio DRY, "Don Repeat
Yourself". Una forma de evitar repetirse, es escribir código reusable, cada vez que
estamos escribiendo nuevo código y tenemos esa sensación de deja-vu de que ya esto lo
hicimos una vez en el pasado, es porque no estamos reusando nuestro código de forma
inteligente. En POO la herencia es una excelente forma de mantener el código reusable sin
mayores repeticiones.
La herencia le permite crear clases que sean refinamientos o especializaciones de otra
clase. Por ejemplo, y siguiendo el ejemplo de Cancion en nuestro reproductor de música
ahora a alguien se le ocurrió que sería interesante que se incluyera el soporte para
canciones de tipo Karaoke. La única diferencia con las otras canciones es que las
canciones Karaoke tienen asociadas la letra de la canción en conjunto con infomación de
sincronización para reproducir las letras del Karaoke en nuestro flamante reproductor
ahora con una gran pantalla de video.
1 class Karaoke < Cancion
2 def initialize(nombre, artista, duracion, letra)
3 super(nombre, artista, duracion)
4 @letra = letra
5 end
6 end
El "< Cancion" en la definición de la clase le indica a Ruby que Karaoke es
un subclase de Cancion, o en dirección opuesta, Cancion es la superclase de Karaoke. De
esta forma la clase hija hereda todos los métodos y declaraciones de variables de su
padre. Al invocar un método sobre un objeto o clase, Ruby defiere su ubicación hasta el
momento de ejecución, en dicho momento Ruby primero mira en la clase para determinar si
existe el método invocado, si no es así, intenta en el padre, y así atravesando todos los
ancestros de la clase hasta ubicar el método invocado. Si se acaban los ancestros donde
buscar, Ruby ejecuta una acción especial que puede ser interceptada si se desea
Object#method_missing, si no, produce un error.
Cada clase especializada maneja sus detalles, para el resto se utiliza super, es decir, el
método del padre o de su ancestro. De esta forma, por ejemplo, en nuestra definición de
Karaoke#initialize dejamos que la inicialización de todo lo común a Cancion ocurra igual
que antes por medio de la llamada a super con los respectivos parámetros necesarios, luego
inicializamos los datos específicos a nuetras clase Karaoke.
---- Espacios de nombres ----
En la medida que escriba programas Ruby cada vez más grandes, usted naturalmente se
encontrará con código reusable, librerías de rutinas relacionadas entre sí por ejemplo.
Usted deseará separar dicho código en distintos archivos separados de tal forma que el
contenido pueda ser reusado entre diferentes programas Ruby. Frecuentemente este código
será organizado en clases.
Otras veces ello simplemente no es conveniente o no aplica, son un grupo de métodos que
desea reusar, usted puede simplemente colocarlos en un archivo y cargar dicho archivo en
su programa con load o require. Esto funciona pero tiene un problema, digamos que se crea
una librería para cocinar con los métodos calentar , mezclar, amasar en un archivo
cocina.rb y otra librería para atletas con los métodos calentar, correr, descansar en el
archivo atleta.rb. Si carga ambos archivos uno después del otro, simplemente el método
calentar colisiona y sólo el más recientemente cargado tendrá la definicón actual del
método, el otro simplemente será olvidado, en resumen la colisión en los nombres es el
problema.
La respuesta es el mecanismo de modulos. Los modulos definen un espacio de nombres en
donde sus métodos y constantes pueden aplicar sin tener que preocuparse en colisionar con
otros métodos y constantes:
1 module Cocina
2 ESCUELA="Latinoamericana"
3 def Cocina.calentar(x)
4 # Se espera que x sea un valor númerico para representar temperatura en oC
5 # ..
6 end
7 ...
8 end
9
10 module Atleta
11 ESCUELA="Simón Bolívar"
12 def Atleta.calentar(t)
13 # Se espera que t sea un valor numérico que represente tiempo en segundos
14 # ..
15 end
16 end
1 >> Cocina::ESCUELA
2 => "Latinoamericana"
3 >> Atleta::ESCUELA
4 => "Simon Bolivar"
5 >> include Atleta
6 => Object
7 >> Atleta.calentar(1000)
8 calentando 1000 segundos
9 => nil
10 >> include Cocina
11 => Object
12 >> Cocina.calentar(10)
13 => 10
Ahora entonces tiene mucho menos probabilidades de provocar colisiones, note que debe
cargar el código, y luego include para usar las funcionalidades del módulo.
---- Herencia múltiples vs Mixins ----
Algunos lenguajes orientados a objetos, tales como C++, soportan herencia múltiple en
donde una clase puede tener más de una superclase heredando funcionalidad de cada una de
ellas. Si bien potente, esta técnica puede ser peligrosa ya que la jerarquía puede tener
ambigüedades. Otros lenguajes como java y C# soportan sólo herencia simple. Si bien más
limpia y simple, la herencia simple también tiene sus desventajas, en la realidad los
objetos heredan atributos de múltiples fuentes en el mundo real.
Ruby ofrece una alternativa interesante y poderosa que le ofrece la simplicidad de la
herencia simple y el poder la herencia múltiple. Una clase Ruby tiene una única clase
padre, en consecuencia Ruby es un lenguaje con herencia simple, sin embargo, las clases
Ruby pueden incluir la funcionalidad de cualquier cantidad de mixins (un mixin es una
especie de definición parcial de clase). Nuevamente dejemos que Ruby hable, creemos
nuestro archivo con la definición de módulo y un par de clases tontas que lo usen como
mixin:
---- mixin_module.rb ----
1 module Debug
2 def quien_soy?
3 "#{self.class.name} (\##{self.objet_id}): #{self.to_s}"
4 end
5 end
6
7 class Cocina
8 include Debug
9 def estilo
10 puts "Italiana"
11 end
12 end
13
14 class Nevera
15 include Debug
16 def capacidad
17 puts "150 pies cúbicos"
18 end
19 end
Si ahora cargamos dichas definiciones de módulo y clases en irb, podemos evidenciar y
experimentar con el uso de los mixins (note que le voy a pasar la forma de hacerlo):
1 $ irb
2 >> load 'mixin_module.rb'
3 => true
4 >> nevera = Nevera.new
5 => #<Nevera:0xb7587b38>
6 >> cocina = Cocina.new
7 => #<Cocina:0xb7585c5c>
8 >> nevera.quien_soy?
9 => "Nevera (#-609469028): #<Nevera:0xb7587b38>"
10 >> cocina.quien_soy?
11 => "Cocina (#-609472978): #<Cocina:0xb7585c5c>"
Bien, es todo por hoy, nos recontraremos en un tercer capítulo dedicado a métodos en una
próxima edición de esta serie dedicada a aprender Ruby.
Este artículo se mantiene en línea en gomix.fedora-ve.org para posibles mejoras y
erratas.
Guillermo Gómez