Ruby

Ruby is a true object oriented programming language.
Ruby is a server-side scripting language similar to Python and PERL.

Ruby can be embedded into HTML.

All ruby files will have extension .rb

#!/usr/bin/ruby  -w
print <<EOF
　　This is the first way of creating
　　here document ie. multiple line string.
EOF

print <<"EOF"; # same as above
　　This is the second way of creating
　　here document ie. multiple line  string.
EOF

print << `EOC` # execute commands
　　echo hi there
　　echo lo there
EOC

print << "foo", <<"bar" # you can stack them
I said foo.
foo
I said bar.
bar

<< can special a string or an identifier to terminate the string literal, and all lines following the current line up to the terminator are the value of the string. Example:

Begin {

} #decalres code to be called before the program is run

End {} #decalres code to be called after the program is run.

Commit:

single Line: #

multi line: =begin    =end

Class and object:

class: class Customer end

Instance variables: using @ prefix the variable name

Class Variables: Class variables are available across different objects. A

using @@ prefix with the clas name

Global Variables: $

Example:

class Customer
    @@no_of_customers =0
end

Creating objects using new method

cust1 = Customer. new
cust2 = Customer. new

def:

define a method: followed by the name of the method, then a list of arguments.

end with a "end"

def load_comics( path )
  comics = {}
  File.foreach(path) do |line|
    name, url = line.split(': ')
    comics[name] = url.strip
  end
  comics
end

Example:

class Customer
@@no_of_customers =0
    def initialize(id, name, addr)
     @cust_id = id
     @cust_name = name
     @cust_addr = addr
    end
end


cust1=Customer .new("1","John","Wisdom Apartments,Ludhiya")

Data:

Integer:

　　-2^30 to 2^(30-1); with Fixnum, Bignum

Floating number: 123.4, 1.0E6, 4E20, 4e+20

String:

using '' or "". You can substitute the value of any Ruby expression into a string using the sequence #{expr}. expr could be any ruby expression.

puts  "Multiplication Value : #{24*60*60}";
Multiplication Value: 86400

Arrays:

using []:  ary = ["a", "This is a string", 3.14, 10, "last element"].

ary.each do |i|

　　puts i

end

 Hash(dictionary)

hsh = colors = {"red" => 0xfoo, "green" => 0x0f0}

Ranges:

Range represents an interval.a set of values with a start and an end.

Ranges constructed uisng ".." run from the start to the end. (1..5) means 1,2,3,4,5

Ranges constructed uisng "..." run from the start to the end excluding the end. (1...5) means 1,2,3,4.

Some special variables:

　　self: The receiver object of the current method.

　　nil: value representing undefined

　　_LINE_: The current line number in the source file/

　　_FILE_: The current file name

Operations:

operator	description	example
<=>	COmbined comparsion operator. Returns 0 if first operand equals second, 1 if operand is greater than the second. -1 if first operand is less than the second.	(a<=>b) returns -1
===	Uesd to test equality within a when clause of a case statement	(1...10) === 5 returns true
.eql?	True if the receiver and argument have both the same type and equal values	1.eql?(1.0) is false
**	Exponent	2**3 is 8
equal?	True if receiver and argument have the same object ID	aObj == bObj
？：	Conditional Expression
defined？

Parallel Assignment:

a,b,c = 10,20,30

Double Colon "::" unary operator tat allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or modules. 

Conditional:

if conditional 
        code...
elsif conditional 
        code...
else code
end

if x>2
    puts "x is greater than 2"
elsif x<=2 and x!=0
    puts "x is 1"
else
    puts  "I can't guess the number"
end

if:

code if condtion

$debig =1
print "debug
" if $debug

#will print debug

Unless:executes the code if conditional is false

unless condition
    code
else 
    code
end

#example

x=1

unless x>2
    puts "x is less than 2"
 else
    puts "x is greater than 2"
end

#result: x is less than 2

Case statements:

case expr0
when expr1, expr2
    stmt1
when expr3, expr4
    stmt2
else
    stmt3
end


$age = 5
case $age
when 0..2
puts "baby"
when 3..6
puts "little child"
when 7..12
puts "child"
when 13..18
puts "youth"
else
puts "adult"
end


#result is "little child"