Constants

constants can’t be changed

EmpireStateBuilding = "350 5th Avenue, NYC, NY"

Objects

Everthing is an object. Objects created via a constructor. Standard constructor is “new”

item_one = LineItem.new

Methods

! and ? can be used in method names

method definition starts with def

def yourage ( dob )
   #code goes here
end

Class Methods

use double colon (creates instance object)

Door::new( :oak )

you can print the an objects type/class

print 5.class                       # prints 'Integer'
print 'wishing for antlers'.class   # prints 'String'
print WishMaker.new.class           # prints 'WishMaker'

accessor methods are created for you.

attr_accessor  :robot1  #creates get/set methods for robot1
attr_reader    :robot2  #creates get method for robot1
attr_writer    :robot3  #creates set method only

privacy is done like this

class Myclass
   def m1   #public method
   end

   protected

   def m2   #this method is protected
   end

   private

   def m3   #this method is private
   end
end

Modules

Hold collection of methods. Act as a namespace. Allow to share funcionality between classes. (

Variables

variables that begin with $ are global

$Chucky_bacon

variables begin with @ are instance variables

@my_chunky_bacon

class variables begin with @@

@@super_chunky_bacon

code blocks can be created with {/} or do/end

2.times { print "Hellow World" }

loop do
   print "Another Hello"
   print "World"
end

you can pass arguments to blocks using the | character

{ |x,y| x + y }

Range

creates range of numbers or chars

(1..3) # numbers 1-3

('a'..'z') # letters a-z

(0...5) # numbers 0-4

Arrays

[1, 2, 3]

['a', 'b', 'c']

Shortcut for creating arrays

a = %w{ a b c }

Hashes

aka dictionary

{'a' => 'apple', 'b' => 'bannana'}

String

Single quoted strings simply contain text, Double quoted strings allow for expression interpolation

print '2+2=#{2+2}' #returns>  2+2=#{2+2}

print "2+2=#{2+2}" #returns>  2+2=4

Double quoted strings that span multiple lines can we written using

%{This sentence
   Spans
   Lots
   Of Lines}

Operators

<<

concatenation operator, appends

email = "tom"
email << "@tomleo.com"

nil?

checks if method is nill. nill is an object.

print( if myfunction.nil?
   "The Function is nill"
else
   "The Function has value!"
end )

==

This is a method

if baconTastesGood.==(true)
   #Yum

if baconTastesGood==(true)
   #Yum

if baconTastesGodd
   #Yum

||

Or operator

a operation b

count += 1
price *= discount
count ||= 0    #count = count || 0

gsub

short for global subsitution

File class

File::read("notefile.txt")
File::rename("oldfile.txt", "newfile.txt")
File::delete("newfile.txt")
File::open('notes.txt', 'w')  #writes to new file
File::open('notes.txt', 'r')  #reads from file
File::open('notes.txt', 'a')  #adds to end of file

Flow of control

case grade
when 100
   "A+"
when 90..99
   "A"
when 80..89
   "B"
when 70..79
   "C"
when 60..69
   "D"
when 0..59
   "F"
end

Regular Expressions (regex)

=~ is the match operator to test strings against regular expressions

if line =~ /P(erl|ython)/
   puts "What other scripting lanuage is work learning?"
end