Some snippets of Ruby on Knowledge Sharing Session -Ruby at Mangoes Mobile

Introduction to Ruby

=begin
author      Eftakhairul Islam <[email protected]> 
website     http://eftakhairul.com
=end

#My First Program at Ruby.

puts 'Hello World'

puts ("I'm here")

#Deffirent between puts and print 

puts ('Here I am again') #Instant flush, $stdout right away And newline automatically.

print ("Here I am again") #Buffering the input,


#Exmaple
5.times { puts "Hello"; sleep 2 }

5.times { print "Hello "; sleep 2 }

STDOUT.sync = true  #You can use STDOUT.flush as well.
5.times { print "hello "; sleep 2 }

1.upto(10) {|i| print i }
('a'..'f').each {|i| print i }

#Common Mathematical terms
=begin

+ plus
- minus
/ slash
* asterisk
% percent
< less-than
> greater-than
<= less-than-equal
>= greater-than-equal

=end

#Exmaple
puts "Is it greater?", 5 > -2

puts 3 + 2 + 1 - 5 + 4 % 2 - 1 / 4 + 6

puts 42.even?



#Variables
cars = 100
puts "There are #{cars} cars available."

language = 'Ruby'
my_height = 74
my_weight = 180 # lbs


puts "Let's talk about %s." % language
puts "He's %d inches tall." % my_height
puts "If I add %d, %d then I will get %d." % [
    my_height, my_weight, my_height + my_weight]

puts "-" * 50

#Some interesting string operations
greeting = "Hello Everyone!"
greeting.delete('l')  #Output: Heo Everyone!

t2 = "sample,data,from,a,CSV"
t2.split(",") #

hello".gsub("ll","y yo") #output: hey yoo

#Array and Hashes
data = ['cat', 'dog', 'ant', 'bee']
data.push('bird')

puts data[0]
#print the whole array
puts data.inspect

#Hash  This is also same to array...In php and ruby array works as hash and array both. Basically, they are  diffeenrt in other language
#Same as above
data = %w{ ant bee cat dog }

data = {
    1 => 'dog',
    2 => 'cat',
    3 => 'bee',
    4 => 'ant'
}

puts data.inspect

restaurantMenu = { "Burger" => 3, "Pizza" => 10, "Coffee" => 2 }

#print key and value
restaurantMenu.each do | item, price |
  puts "#{item}: $#{price}"
end

#return all keys
puts restaurantMenu.keys

#another way to create hash
my_hash = Hash.new
my_hash['burger'] = 3

print my_hash['burger'] #output will be 3

#Loop

#normal while
i   = 0;
num = 5;

while i < num  do
  puts("Inside the loop i = #{i}" );
  i +=1;
end


#do while

i = 0;
num = 5;
begin
  puts("Inside the loop i = #{i}" );
  i +=1;
end while i < num


#for
for i in 1..5
  puts "Value of local variable is #{i}"
end


#each
(0..5).each do |i|
  puts "Value of local variable is #{i}"
end

(0..5).each  {|i| puts "Value of local variable is #{i}"}

family = { "Homer" => "dad",
  "Marge" => "mom",
  "Lisa" => "sister",
  "Maggie" => "sister",
  "Abe" => "grandpa",
  "Santa's Little Helper" => "dog"
}

family.each { |x, y| puts "#{x}: #{y}" } #it prints both key and value

 until counter == 0
     puts "The counter is #{counter}"
     counter = counter - 
 end


#Regular Expression
line = 'Perl'
if line =~ /Perl|Python/   #Basically regular expression by writing a pattern between   slash characters (/pattern/)
  puts "Scripting language mentioned: #{line}"
end


#Introduction to Function

def printCurrentTime()

  time = Time.new
  return time.ctime
end


def printName( name )
  puts "My name is: #{name.capitalize}."
end


def printAllNames( *args )
  arg1, arg2 = args  
  puts "Name-1: #{arg1}, Name-2: #{arg2}"
end


puts printCurrentTime()
printName( "Eliza" )
printAllNames( "Tahins", "Eftakhairul" )

#OOP
class BookInStock
  @isbn
  @price

  @@count = 0

  attr_reader :price
 

  def initialize(isbn, price)
    @isbn = isbn
    @price = Float(price)
    @@count += 1
  end

  def price=(newPrice)
    @price  = newPrice
  end

  def isbn
    @isbn
  end

  private
  def printName
    puts 'My Name is Ruby lolz!!! Stupid I am not human'
  end

  public
  def to_s
    "ISBN: #{@isbn}, price: #{@price}"
  end

  def printAll
    printName
  end

  def self.printCount()
    puts "Box count is : #@@count"
  end

end


book 		= BookInStock.new('BN123', 12)
book.price 	= 10

puts book.price
puts book.to_s
puts book.printAll

book2   	= BookInStock.new('BC100', 12)
book3   	= BookInStock.new('BD200', 12)

BookInStock.printCount()


class Box

  BOX_COMPANY = "BD Box Ltd."

  def initialize(w,h)
    @width, @height = w, h
  end

  def getArea
    @width * @height
  end
end

# define a subclass
class BigBox < Box

  # add a new instance method
  def printArea
    @area = @width * @height
    puts "Big box area is : #@area"
  end
end

# create an object
box = BigBox.new(10, 20)

# print the area
box.printArea()

puts "Company Name: #{BigBox::BOX_COMPANY}"

#Diff btw @@ and @
@@ -> class variable; It's available through all classess and extended class. it's kind of java's static variable
@  -> instance variable; It's only available class's lexical scope. 


#Taking input from commandline
STDOUT.flush
print "How old are you? "
age = gets.chomp()
puts "So, you're #{age} old."

first, second, third = ARGV

puts "The script is called: #{$0}"
puts "Your first variable is: #{first}"
puts "Your second variable is: #{second}"
puts "Your third variable is: #{third}"



#Importing library
require 'open-uri'

open("http://eftakhairul.com") do |f|
  f.each_line {|line| p line}
end


#Open, read AND write file
if File.exists?('hello.txt')
  txt = File.open('hello.txt')
  puts txt.read()
else
  puts 'File not found.'
end



#More details @ http://ruby-doc.org/core-1.9.3/File.html

#Debuging function
abort("Message goes here")

#OR

puts "Message goes here"
exit

#Another best way to debug 
raise Object.inspect