Test ruby

ruby test

1) Explain calling super and calling super() and give some example?
      super and super() both inherits methods from parent class. super allows the arguments but super() dont allow the arguments.
      Ex:
      --
         class Niyati
           def process(person,work)
              "I am #{person} and am a #{work}"
           end
         end
         
         class Ror < Niyati
           def process()
             super
           end
         end
         =>
         Ror.new.process("prasanth","ROR developer")
         =>
         I am prasanth and am a ROR developer
         
         class Ruby < Niyati
           def process(person,work)
             super()
           end
         end
         =>
         Ruby.new.process("velu","ROR developer")
         =>
         Argument error given 0 expected 2
         ---------------------------------
  2)     when they should be used: ==, ===, eql?, equal? and give some example
            These are equality operators and methods in ruby. It compares the strings length and content equal or not.
            Methods only checks the values with same type. But, == and === are return true if values are the same not forces the same type.
            Ex:
              1 == 1.0, 1 === 1.0 => true
              1.eql? 1.0 => false "12".length.equal? "ab".length =>true
   3)     tell diff for array.map(&:method_name) as a shorthand form of array.map { |element| element.method_name }. How exactly does it work?
             In &:method_name, & is a unary operator which helps to convert method into proc_block. 
             Ex:
             --
             arr = ['a','b','c']
             arr.map(&:upcase)
             =>
             ['A','B','C']
    4) Find the below code

           class A
             def self.a(b)
               if b > 0
                  b * b
               end
             end
           end

           what will be output of

           var1 = A.a(0)
           var2 = A.a(2)
           output:
           ---
           Calling self method using A.a(0), which returns nil because the condition is false. 
           => A.a(0) = nil
           => A.a(2) = 4
        
      5)   Can you call a private method outside a Ruby class using its object, give example?
        
               Cant call the private method directly outside ruby class using object,it returns NoMethodError.
           But we can use send method to access all the instance methods of current object.
           Ex:
           ---
           class Klass
             def pub
               "I'm Public"
             end
             private
                def pri 
                  "I'm private"
                end
            end
            Output:
            -----
              Klass.new.pri
              => NoMethodError private method pri
              obj = Klass.new
              obj.send(:pri)
              =>
              I'm private
            
           end
      
      6)  Difference between clone and du
             Clone and dup both used to create a shallow copy of object. But clone differ in 2 things.
             1) freeze 2) maintain the singleton methods
             Ex:
             ---
             [freeze]
             a = [12,34,55,66,77]
             a.freeze
             b = a.clone
             c = a.dup
             b << 6
             =>
             Cant modify frozen array.
             c << 6
             => 12,34,55,66,77,6]
             [singledon methods]
             obj = Object.new
             def obj.iam
               "I'm velu"
             end
             b = obj.clone
             b.iam
             => 
             "velu"
             c = obj.dup
             c.iam
             =>
             NoMethodError 
             
   7)      how can achieve method overloading in ruby give some example?
            To achieve method overloading, we should use two different versions of method with same name. But ruby class can have only one method with same name.
          By achieve this we can pass many arguments with the single method.
          Ex:
          ---
          def some(*p)
           if p.size < 2
              "less than"
           else
              "many arguments"
           end
         end
         
     
    8)    diff b/w if vs unless vs untill give some example?
          Unless and until both are false block statement. When condition is false its block code is executed, when true it terminated.
          Ex:
          --
          i = 5
          until i >= 10
            p i
            i += 1
          end
    
    9)    super keyword
          Super method calls the parent method of the same name, and also with the same arguments.
          
    
    10) three levels of method access control give some example ?
        => Public - Can access by everyone
        => private - Can access by implicit receiver only
        => protected - Can access by explicit reciever also
        class Klass
        def m
         m1
        end
        private
        def m1
          "#{self.class}"
        end
        protected
        def m2
          "#{self.class}"
        end
       end
       --
       class Hlass < Klass
         def m
           m1
         end
       end
       ---
       
      11) module vs class
          In module is a collection of instance methods that included or extended to class. Mixin is best example for module.
          We can create the instantiated object in class and also we can inherit the class to another class.
          
          module Ror
            def process
              "learning"
             end
          end
          
          class Niyati
             include Ror
          end
          
          Niyati.new.Ror
          => learning
      
      12) proc vs lambda
          ------
          => lambda is a proc object
          => lambda expects correct arguments to pass in method, otherwise it returns argument error
    
      15) Find duplication element in array
         a = ["A", "B", "B", "C", "A", "a", "c"]
         b = a.group_by { |a| a }
         b.keep_if { |k,v| v.length > 1 }
         => 
         [A,A],[B,B}
         a.uniq
         => which eliminates the duplicate values.
     
     16) reverse a given string
         h1 = "my name is abc"
         h2 = h1.reverse
         h2.split(' ' ).map(&:reverse).join(' ' )
          
          
      17) Array mixing with string, hash  and integer number need to arranging order  
          a = [3, 1, "C", {:name=>"hari"}, "A"]
          a.sort_by { |a| a.to_s }
          =>
          [1,3,"A","C", {:name => "hari" }
          
     18) find the most repeat value and count 
         my_val = [1,1,1, 2,2,2, 5,5, 2,2,2]
         freq = my_val.uniq.max_by { |i| my_val.count(i) }
         p freq 
         => 
         2
    19) write a regular expression Input value should allow 5 integer 1 character should not allow any special character  
        
        => /(\d{5})+(\D{1})/
         
     20)  write a regular expression for email  
     
           /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/