Rails Introduction

• Try out the tools of the trade
  
• Get a feeling for the steps involved
• See that you can too

$git --versiongit version 1.8.3.4 (Apple Git-47)

$ruby -vruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.5.0]$irb2.0.0-p247 :002 > 2+2
 => 4 
2.0.0-p247 :005 > require 'active_support/all'
 => true 
2.0.0-p247 :006 > 1.day.ago
 => 2013-10-16 17:49:11 +0200 

$sqlite3
SQLite version 3.7.12 2012-04-03 19:43:07
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> .quit

$heroku version
heroku-toolbelt/3.0.0 (x86_64-darwin10.8.0) ruby/1.9.3$heroku login
Enter your Heroku credentials.
Email: your_email@gmail.com
Password (typing will be hidden): 
Authentication successful.

• Model: Concept + Save objects
  
• View: What user sees
  
• Controller: What user does
  

> 6 => 6 
> 6.5
 => 6.5  

> Bob
NameError: uninitialized constant Bob
	from (irb):45
	from /Users/gdj/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in `'
> "Bob"
 => "Bob" 
> :Bob
 => :Bob

> 6.even? # Ruby ignores anything after '#' => true 
> 6.5.even? # Ruby understands first dot is decimalNoMethodError: undefined method `even?' for 6.5:Float
	from (irb):50
	from /Users/gdj/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in
> 6.+( 7 ) # Method with argument
 => 13 
> 6.5.+ 7 # You can add integer to float. And skip par.
 => 13.5 
> 6 + 7 # This is the same as 6.+( 7 )
 => 13

> x
NameError: undefined local variable or method `x' for main:Object
	from (irb):31
	from /Users/gdj/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in 
> x = 6
 => 6 
> x
 => 6 
> x = 7 # x is changed to a different value (x is a variable)
 => 7 
> x + 6
 => 13 
> recipient = "Bob"
 => "Bob" 
> recipient + "@gmail.com"
 => "Bob@gmail.com" 

> ingredients = ["milk", "eggs", "flour", "oil" , "salt"]
 => ["milk", "eggs", "flour", "oil", "salt"] 
> ingredients.first
 => "milk"
> ingredients[4] # This is just a method call. Looks funny.
 => "salt"

> recipe = {:milk => "2dl", :eggs => 2, :flour => "1hg"}
 => {:milk=>"2dl", :eggs=>2, :flour=>"1hg"} 
> recipe.size
 => 3 
> recipe[:eggs] # This is also a method call 
 => 2 

'> "Bob".class
 => String 
> :Bob.class
 => Symbol

'> ingredients.class
 => Array 
> recipe.class
 => Hash

> recipient
 => "Bob" 
> recipient.concat "@example.com"
 => "Bob@example.com" 
> recipient
 => "Bob@example.com"> recipe[:salt] = "1pinch"
 => "1pinch" 
> recipe
 => {:milk=>"2dl", :eggs=>2, :flour=>"1hg", :salt=>"1pinch"}

> fahr = 90
 => 90 
> celsius = (5.0/9.0) * (fahr - 32)
 => 32.22222222222222 
> fahr = 80
 => 80 
> celsius = (5.0/9.0) * (fahr - 32)
 => 26.666666666666668 

> def fahr_to_celsius( fahr )
>   (5.0/9.0) * (fahr - 32)
> end
 => nil 
> fahr_to_celsius 80
 => 26.666666666666668 
> fahr_to_celsius 70
 => 21.11111111111111