1. RUBYRUBY

2. Ruby Classes and Objects Defining a Class: class Example end Creating Objects: ex1=Example.new ex2=Example.new Example: class Customer @@no_of_customers=0 def initialize(id, name, addr) @cust_id=id @cust_name=name @cust_addr=addr end end 3. Example for Class and Object We declare the initialize method with id, name, and addr as local variables. In the initialize method, we pass on the values of these local variables to the instance variables @cust_id, @cust_name, and @cust_addr. Now, we can create objects: cust1=Customer.new("1", "Alex", "Coimbatore, TN") cust2=Customer.new("2", "Balu", "Chennai, TN") 4. Member Functions in Ruby Class In Ruby, functions are called methods. Each method in a class starts with the keyword def followed by the method name and end with the keyword end. Example: class Sample def hello puts "Hello Ruby!" end end object = Sample. new object.hello //=> Hello Ruby! 5. Example for Class and Odject class Customer def initialize(id, name, addr) @cust_id=id @cust_name=name @cust_addr=addr end def display_details() puts "Customer id #@cust_id" puts "Customer name #@cust_name" puts "Customer address #@cust_addr" end end cust1=Customer.new("1", "Alex", "Coimbatore, TN") cust2=Customer.new("2", "Balu", "Chennai, TN") cust1.display_details() cust1.total_no_of_customers() cust2.display_details() cust2.total_no_of_customers() Output: Customer id 1 Customer name Alex Customer address Coimbatore,TN Customer id 2 Customer name Balu Customer address Chennai,TN 6. Class Inheritance Inheritance From Base Class: class Parent def implicit() puts "Hello Parent" end end class Child < Parent end dad = Parent.new() son = Child.new() dad.implicit() son.implicit() Output: Hello Parent Hello Parent 7. Inheritance Example class Parent def override() puts "Hi Parent" end end class Child < Parent def override() puts "Hi Child" end end dad = Parent.new() son = Child.new() dad.override() son.override() Output: Hi Parent Hi Child 8. Ruby Variables Ruby Global Variables: Global variables begin with $. Example: $global_variable=100 Ruby Instance Variables: Instance variables begin with @. Example: @instance_variable=200 Ruby Class Variables: Class variables begin with @@ and must be initialized before they can be used in method definitions. Example: @@class_variable=300 9. Ruby Arrays Creating an Array: a=[1,2,3,4,5] ( or) ary=Array.new ary[0]=1 ary[1]=2 ary[2]=3 arr = ['a', 'b', 'c', 'd', 'e', 'f'] 10. Accessing Array Accessing Element: arr = [1, 2, 3, 4, 5, 6] arr[2] # 3 arr[100] # nil arr[-3] # 4 arr[2, 3] #[3, 4, 5] arr[1..4] #[2, 3, 4, 5] arr.take(3) # [1, 2, 3] arr.drop(3) # [4, 5, 6] arr.at(0) # 1 arr.first # 1 arr.last # 6 11. Adding Items to Arrays For adding can use either push or 10, "Balu" => 6 } grade=Hash["a", 100, "b", 200] grade=Hash["a" => 100, "b" => 200] h = Hash.new() h["a"] = 100 h["b"] = 200 h #{"a"=>100, "b"=>200} Accessing Hash: h = { "a" => 100, "b" => 200 } h[a] # 100 h[c] # nil h[b] #200 19. .each in Hash h = { "a" => 100, "b" => 200 } h.each { |key, value| puts "#{key} is #{value}" } Output: a is 100 b is 200 h = { "a" => 100, "b" => 200 } h.each_key {|key| puts key } Output: a b h = { "a" => 100, "b" => 200 } h.each_value {|value| puts value } Output: 100 200 h.has_key?("a") #true h.has_key?("z") #false h.has_value?(100) # true h.has_value?(999) # false 20. Ruby if,Else if Stmt Ruby If: if var == 10 print Variable is 10 end Ruby Else If: x=5 if x > 2 puts "x is greater than 2" elsif x 2 puts "x is less than 2" else puts "x is greater than 2" end #x is greater than 2 21. Hash Example with argument def hash_arg(opt={}) alpha={ :a=>'Apple', :b=>'Banana', :c=>'Carrot', :d=>'Dog' }.merge(opt) puts "#{alpha[:a]} #{alpha[:b]} #{alpha[:c]} #{alpha[:d]}" puts opt puts alpha end hash_arg() hash_arg(:e => 'and') Output: Apple Banana Carrot Dog {} {:a=>"Apple", :b=>"Banana", :c=>"Carrot", :d=>"Dog"} Apple Banana Carrot Dog {:e=>"and"} {:a=>"Apple", :b=>"Banana", :c=>"Carrot", :d=>"Dog", :e=>"and"} 22. Case Statement Case Stmt: 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 Output: little child 23. While and For loop While Loop: i = 0 while i < 5 do puts "Inside the loop i = #{i}" i +=1 end Output: Inside the loop i = 0 Inside the loop i = 1 Inside the loop i = 2 Inside the loop i = 3 Inside the loop i = 4 For Loop: array=[0,1,2,3,4,5] for i in array puts "Value of i is #{i}" end Output: Value of local variable is 0 Value of local variable is 1 Value of local variable is 2 Value of local variable is 3 Value of local variable is 4 Value of local variable is 5 24. Methods in Ruby Defining a Method with default argument: def test(a1="Ruby", a2="Java") puts "The programming language is #{a1}" puts "The programming language is #{a2}" end test "C", "C++" test Output: The programming language is C The programming language is C++ The programming language is Ruby The programming language is Java Defining a Method with Multiple argument: def some_method(a,b,*c,d) puts "A contain #{a}" puts "B contain #{b}" puts "c contain #{c}" puts "D contain #{d}" end some_method(5,4,2,1,6,7,8,9,3) Output A contain 5 B contain 4 c contain [2, 1, 6, 7, 8, 9] D contain 3 25. Ruby Blocks Example: def test puts "You are in the method" yield puts "You are again back to the method" yield end test { puts "You are in the block" } Output: You are in the method You are in the block You are again back to the method You are in the block 26. Ruby Blocks in Class Example: class Own_class < Array def double_each self.each do |element| yield(element*2) end end end d=Own_class.new([10, 20, 30, 40, 50]) d.double_each { |x| puts x } Output: 20 40 60 80 100 27. THANK YOUTHANK YOU