Ruby on Rails/Utskriftsversjon

Introduksjon

Velkommen til Ruby on Rails-boken!

Ruby on Rails er et MVC-rammeverk tilrettelagt for utvikling av nett-programmer. Det benytter språkene Ruby og YAML. Denne boken tar for seg dette rammeverket, og beskriver dets metoder og bruk, fra nybegynner til profesjonell.

Den antar at leseren har en grunnleggende forståelse for programmering, og kjenner til grunnleggende HTML/CSS. Disse er basiskunnskaper for å lage nett-programmer, og det antas kompetanse innenfor disse områdene i så godt som alle rammeverk for nett-programmering.

Boken er lagd for å leses fra start til slutt. Man bør forstå det som står i kapittel 2 for å lese kapittel 3 osv.

Kodeeksempler

Kodeeksempler vil se slik ut:

"Dette er en test."

Noen eksepler vil også vises "i ett med teksten".

Dersom koden i kodeeksemplene returnerer en eller annen verdi når koden blir kjørt, vil det vises på denne måten:

5 + 2
=> 7

"Test test" + " og test."
=> "Test test og test."

Dersom man kopierer koden i eksemplet, vil den ikke nødvendigvis returnere noe. Men for eksemplenes skyld lar vi "=>" indikere hva som kunne ha blitt returnert.

Installasjon

Linux

Det er nok trygt å anta at en som bruker Linux kan litt av hvert om installering av programvare. Derfor vil retningslinjene for hvordan man skal få det til være ganske generelle. Referer til http://google.com og andre kilder for distribusjons-spesifikke retningslinjer.

Først må Ruby og RubyGems installeres. Disse kan enten kompileres på egen hånd eller installeres via pakkebehandlingssystemet (apt-get, dpkg etc). Husk at Readline må installeres før man kompilerer Ruby for at IRb og andre verktøy skal virke. Når RubyGems er installert, kjøres sudo gem install rails --include-dependencies for å installere Rails.

Merk at det er vanlig at binaries man installerer med RubyGems legger seg i RubyGems sin egen bin-mappe. Denne må legges i $PATH for at rails-kommandoen skal virke på samme måte som denne boken bruker den.

Windows

• Installer Ruby og Ruby Gems(med http://rubyforge.org/projects/rubyinstaller/)
• Bruk Ruby Gems til å installere Rails og alle dens "depenencies".

OS X

NB: Neste versjon av OS X, 10.5, vil ha Ruby on Rails ferdiginstallert.

Kompileringsverktøy

Man kan installere Rails ved hjelp av Fink, MacPorts eller ved å kompilere på egen hånd. Uansett hvilket alternativ som velges, trengs et kompileringsverktøy. Når man bruker Fink/MacPorts, gjør man (som oftest) teknisk sett det samme som å kompilere selv, bortsett fra at automatiseringsverktøyet tar seg av nedlasting av filer, installering av annen programvare det man installerer er avhengig av etc. Når man kompilerer selv, uten å bruke Fink/MacPorts, vil man også trenge et kompileringsverktøy.

Det enklest tilgjengelige kompileringsverktøyet for OS X er GCC, GNU Compiler Collection. GCC følger med Apples Xcode-pakke, som kan lastes ned fra http://developer.apple.com.

Etter å ha registrert seg (helt gratis), naviger til https://connect.apple.com/cgi-bin/WebObjects/MemberSite.woa/wa/getSoftware?bundleID=19681, logg inn, og last ned. Kjør Xcode-installasjonen, og installer. Det er ikke nødvendig å installere hele Xcode-pakken, det holder å installere Xcode-hoveddelen og GCC.

Man kan også installere GCC via MacPorts.

Kompilere selv

(Takk til http://hivelogic.com/narrative/articles/ruby-rails-mongrel-mysql-osx)

Legg til følgende i filen ~/.bash_login:

export PATH="/usr/local/bin:/usr/local/sbin:/usr/local/mysql/bin:$PATH"

Last ned nyeste versjon av w:Readline fra ftp://ftp.gnu.org/gnu/readline/:

wget ftp://ftp.gnu.org/gnu/readline/readline-XX.tar.gz

Pakk ut og kompiler:

tar xzvf readline-XX.tar.gz
cd readline-XX
./configure --prefix=/usr/local
make
sudo make install

Passordet sudo spør om er det samme passordet som er knyttet til brukerkontoen i OS X. Med andre ord, det man bruker til å logge inn, installere programvare etc.

Last ned nyeste versjon av Ruby fra http://ruby-lang.org (bruk URL-en fra ruby-lang.org, ikke den i eksemplet nedenfor).

wget ftp://ftp.ruby-lang.org/pub/ruby/XX/ruby-XX.tar.gz

Pakk ut og kompiler:

tar xzvf ruby-XX.tar.gz
cd ruby-XX
./configure --prefix=/usr/local --enable-pthread --with-readline-dir=/usr/local --enable-shared
make
sudo make install

Last ned og kompiler RubyGems fra http://rubyforge.org/projects/rubygems/

wget http://rubyforge.org/frs/download.php/20989/rubygems-XX.tgz
tar xzvf rubygems-XX.tar.gz
cd rubygems-XX.tar.gz
sudo sudo /usr/local/bin/ruby setup.rb

Dermed kan man bruke RubyGems til å installere Ruby on Rails.

sudo gem install rails --include-dependencies

Fink

...

MacPorts

...

Grunnleggende Ruby

Objekter

Så godt som alt i Ruby er et objekt. Mange har forsøkt å forklare hva et objekt er, men de aller fleste ender opp med å bli innlagt på et mentalsykehus. Kort sagt: poenget med objekter er å modellere virkeligheten. Dersom et objekt har en lengde, ligger informasjonen om lengden i selve objektet. Man trenger ikke en ekstern funksjon for å vite hvor langt det er. (Dette trenger sårt en bedre forklaring.)

Alle objekter har en klasse, og klassen definerer hva slags objekt det er.

5.class
=> Integer #(En Integer er et tall uten desimaler)

"Dette er en tekst".class
=> String #(en String er en samling tekst, symboler tall etc.

["Fiolin", "Gitar", "Tuba"].class
=> Array #(et Array er en samling av objekter)

#Og alt etter '#' blir ansett som en kommentar, og vil ikke bli
#lest som Ruby-kode.

Alle «tingene» (som 5, Dette er en tekst etc) har en klasse. Eksempler på klasser er Integer (tall uten desimaler) og String (tekstsbiter med tall, symboler etc). Klassen til objektet definerer hva slags type objekt det er, og hva du kan gjøre med det.

Med ett Integer-objekt kan man gjøre typiske numeriske kalkulasjoner.

1 + 2
=> 3

6 - 1 
=> 5

8 / 2
=> 4

Ett String-objekt oppfører seg annerledes, siden det er av en annen klasse.

"Hei på deg".upcase
=> "HEI PÅ DEG"

"Snakke baklengs".reverse
=>"sgnelkab ekkanS"

"Legg meg" + " til deg."
=> "Legg meg til deg."

"5" + "2"
=> "52"

Metoder

Metoder er beskjeder man sender til objekter.

Det finnes to ulike typer metoder. Klassemetoder og instansmetoder. Klassemetoder kaller man direkte på en klasse, som String, mens instansemetoder kalles på en instans av noe. new er en klassemetode av String, mens upcase er en instansmetode av String.

Logikken er at klassemetoder gir funksjonalitet som går direkte på klassen.

Lag klasser

Klassene String og Integer er innebygd i Ruby. I Ruby kan man også lage nye klasser, og gi dem egenskaper.

class Vehicle
  def move_forward
    "moving forward"
  end

  def stop
    "stopped"
  end
end

def er et nøkkelord (end og class er også nøkkelord) for å definere en metode. Det som står etter def er navnet på metoden, i dette tilfellet move_forward og stop.

Slik virker den nye klassen:

#Lag en instans av Vehicle
vehicle = Vehicle.new

vehicle.class
=> Vehicle

vehicle.move_forward
=> "moving forward"

Arving av egenskaper

En klasse kan være en underklasse av en annen klasse. En underklasse vil arve alle egenskapene til klassen den er underklasse av.

class Bicycle < Vehicle
  def ring_bell
    "pling plong"
  end

  def pedal
    "pedaling"
  end
end

Det kan brukes på denne måten.

bicycle = Bicycle.new

bicycle.ring_bell
=> "pling plong"

# arver metoder fra over-klassen
bicycle.stop
=> "stopped"

bicycle.tullball
=> NoMethodError: "undefined method ‘tullball’ for Vehicle"

Metoden stop ble ikke definert i klassen Bicycle. Den metoden arvet Bicycle fra Vehicle.

Ruby har et helt sett med innebygde klasser. Kernel ligger på topp, og definerer nøkkelordene som def, return, class. Kernel sin underklasse Object definerer metoder som ettellerannet.class, og andre liknende «globale» metoder, som ettellerannent.object_id, ettellerannet.send, ettelerannet.inspect osv.

I stedet for å skrive ettellerannet.metode for å referere til en instansmetode, er det vanlig å bruke Klasse#metode. Så, dersom den forestilte klassen Queue har instansemetoden move_forward og klassemetoden find_all, kan man referere til dette som Queue#move_forward og Queue.find_all. Dette kan ikke brukes på denne måten i selve språket, da # definerer en kommentar i koden. Det man ville skrevet som Queue#move_forward vil i virkeligheten bli skrevet slik:

queue_item = Queue.new
queue_item.move_forward

Lagring av data

Et objekt kan settes opp slik at det inneholder data.

class Vehicle
  def initialize(brand, horse_power)
    @brand = brand
    @horse_power = horse_power
  end

  def brand
    @brand
  end
  
  def horse_power
    @horse_power
  end
end

initialize-metoden har Vehicle arvet fra Object-klassen. Den brukes til å definere hva som skal skje når man lager en ny instans av klassen man definerer den i.

Variabler som @ser_ut_som_dette er instansvariabler. De er tilgjengelige i den instansen av klassen de er satt i.

not_working = Vehicle.new
=> ArgumentError: "wrong number of arguments (0 for 2)"

my_car = Vehicle.new("Volvo", 192)

my_car.horse_power
=> 192

Logisk nok deles ikke verdiene på tvers av instanser.

v1 = Vehicle.new("Subaru", 110)
v2 = Vehicle.new("Fiat", 97)

v1.horse_power
=> 110

v2.horse_power
=> 97

Det finnes også funksjonalitet for å redigere data etter instansen er laget.

class Vehicle
  def initialize(brand, horse_power)
    @brand = brand
    @horse_power = horse_power
  end

  def brand
    @brand
  end
  
  def horse_power
    @horse_power
  end

  def set_brand(brand)
    @brand = brand
  end

  def set_horse_power(horse_power)
    @horse_power = horse_power
  end
end

Dette kan brukes på følgende måte:

my_bmw = Vehicle.new("BMW", 182)

my_bmw.horse_power
=> 182

my_bmw.set_horse_power(212)
my_bmw.horse_power
=> 212

I de aller fleste tilfeller ønsker man å gjøre my_bmw.horse_power = 138. For å sette opp dette, definer metonede på følgende måte:

class Vehicle
  def horse_power=(horse_power)
    @horse_power = horse_power
  end
end

my_saab = Vehicle.new("saab", 177)
my_saab.horse_power = 172
my_saab.horse_power
=> 172

Siden det er ganske tungvint å skrive alle disse metodene - særlig hvis man har mange attributter - finnes det snarveier for å sette opp en klasse på denne måten med attr_reader, attr_writer og attr_accessor.

class Vehicle
  # definerer Vehicle#brand og Vehicle#horse_power
  attr_reader :brand, :horse_power
  # definerer Vehicle#max_speed=
  attr_writer :max_speed
  # defivener Vehicle#weight og Vehicle#weight=
  attr_accessor :weight

  def initialize(brand, horse_power)
    @brand = brand
    @horse_power = horse_power
  end

  # Siden @max_speed bare er satt med attr_writer, defineres
  # denne metoden for å vise verdien av @max_speed
  def max_speed
    @max_speed
  end
end

a_truck = Vehicle.new("Scania", 496)
a_truck.horse_power
=> 496

a_truck.max_speed
=> nil

a_truck.max_speed = 120
a_truck.max_speed
=> 120

a_truck.weight = 8000
a_truck.weight
=> 8000

Grunnleggende Rails

Rammeverket Ruby on Rails

Om de ulike mappene/filene som genereres med rails-kommandoen.

Rails er Ruby

Om hvordan ActiveRecord::Base brukes for å gi modellene egenskaper. Ulike klasse/instans-metoder for modeller. Det samme med kontrollere.

GNU Free Documentation License

Beskyttet: Kopi av gjeldende lisens ifølge brukervilkårene. Kun administratorer har tilgang til å redigere eller flytte siden.

GNU Free Documentation License

Version 1.3, 3 November 2008

Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. https://fsf.org

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

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Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/licenses/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A "Massive Multiauthor Collaboration" (or "MMC") contained in the site means any set of copyrightable works thus published on the MMC site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or in part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this:

with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.