Practise from Well grounded Rubyist

practise_1.rb

class C
  puts "Just started class C"
  puts self

  module M
    puts "Nested module C::M"
    puts self
  end

  puts "back in the outer level of C:"
  puts self
end

class D
  def x
    puts "Class D, method x:"
    puts self
  end
end

d = D.new
d.x
puts "That was a call to x by #{d}"

obj = Object.new
def obj.show_me
  puts "Inside Singlton method show_me of #{self}"
end

obj.show_me
puts "Back from call to show_me by #{obj}"

class E
  def E.no_dot #Also self.no_dot
    puts "As long as self is E, you can call this method with no dot"
  end

  no_dot
end

#E.no_dot

class F
  def x
    puts "This is a method 'x'"
  end

  def y
    puts "This is a method 'y', abdout to call x without a dot"
    x
  end
end

  f = F.new
  f.y

class Person_1
  attr_accessor :first_name, :middle_name, :last_name

  def whole_name
    n = first_name + " "
    n << "#{middle_name}" if middle_name
    n << last_name
  end
end

goliath = Person_1.new
goliath.first_name = "Goliath"
goliath.last_name = "Black"

 puts "Goliath's whole name: #{goliath.whole_name}"

goliath.middle_name = "Alan"

puts "David's whole name: #{goliath.whole_name}"

class G
  puts "Just inside class definition block. Here's self"
  p self

  @v = "I'm an instance variable at the top level of class G"
  puts "And here's the instance variable @v, belonging to #{self}"
  p @v

  def show_var
    puts "Inside an instance method definition block, here's self:"
    p self
    puts "And here's the instance variable @v, belonging to #{self}"
    p @v
  end
end

g = G.new
g.show_var

h = 0

def top
  puts "top level method TOP"
end

class I
  h = 1 #EACH H KNOWS NOTHING OF THE OTHERS
  def self.x
    h = 2
    puts "I.x; h = #{h}"
  end

  def m
    h = 3
    puts "I-object.m; h = #{h}"
  end

  def n
    h = 4
    puts "I-object.n; h = #{h}"
  end
  puts h
end

puts "Top level h = #{h}"
I.x
j = I.new
j.m
j.n

class K
  def  x(value_for_a, recurse=false)
    a = value_for_a
    print "

    Here's the object_id string for 'self': "
    p self.object_id
    puts "and here's a: "
    puts a
    if recurse
      puts "recursing by calling myself..."
      x("second value for a")
      puts "Back after recursion, here's a:"
      puts a
    end
  end
end

k = K.new
k.x("First value for a")
k.x("First value for a with recursion", true)

class Violin
  class String
    attr_accessor :pitch
    def initialize(pitch)
      @pitch = pitch
    end
  end

  def initialize
    @e = String.new("E")
    @a = String.new("A")
  end
end

v = Violin.new