A look into object_id

01.str.rb

# Date Created: 17 June 2021
# Ruby Version 3.0.0p

def object_id_of_str obj_1, obj_2
  # The argument has same object_id as original object because..
  # ..it refers to same object, it doesn't copy objects' value but it points..
  # ..to original objects' memory, hence holding objects' reference ID in the memory
  puts "Before modification, object 1 ID: #{obj_1.object_id}" # => 60
  puts "Before modification, object 2 ID: #{obj_2.object_id}" # => 80

  # << operator changes value in the same memory location, modifying original obj
  obj_1 << " there"
  # same id
  puts "After modification, object 1 ID: #{obj_1.object_id}" # => 60

  # = operator creates new object in memory
  obj_2 = "TADA"
  # since location is different in memory, id will be too
  puts "After modification, object 2 ID: #{obj_2.object_id}"  # => 100
end

str_1 = "Hi"
str_2 = "Bye"
puts "Object ID of #{str_1}: #{str_1.object_id}" # => 60
puts "Object ID of #{str_2}: #{str_2.object_id}" # => 80

# calling function and passing above strings as arguments
object_id_of_str(str_1, str_2)

# AFTER Function call----
#
# The modification of object in function happened to original object..
# .. hence its value is now changed
puts "String 1 = #{str_1}" # => Hi there
# the original object does not get modified hence same value
puts "String 2 = #{str_2}"  # => Bye

02.array.rb

def object_id_of_array obj
  # original object id
  puts "#{obj} = #{obj.object_id}" # => [1, 2, 3] = 60

  # .dup creates new objectwith different memeory address with same value as original obj
  obj = obj.dup
  # hence different id
  puts "Duplicate object #{obj} = #{obj.object_id}" # => [1, 2, 3] = 80

  # appends new value
  obj << "Extra"
  puts "Duplicate object :#{obj}" # => [1, 2, 3, "Extra"]

  # = operator cannot modify original obj because we are refering to different object and not original objects' id
  obj = ["new value"]
  puts "Duplicate object :#{obj}" # => ["new value"]
end


a = [1,2,3]

# calling function
object_id_of_array(a)

# original object isn't modified
puts "Original object: #{a}"  # => [1, 2, 3]

03.deep_duplication_array.rb

a = [1,2,3]
puts "Original array id:#{a.object_id}" # => 60


# an array within an array
nest = [a]
puts "nested array value:#{nest}" # => [[1, 2, 3]]
# different array ID
puts "nested array id:#{nest.object_id}"  # => 80
# inner array has same ID as Original array
puts "Inner array id:#{nest[0].object_id}"  # => 60


# duplicating nest array, which will give same value but different object_id
nest_dup = nest.dup
# different array ID
puts "duplicate array id:#{nest_dup.object_id}" # => 100
# but not for inner array
puts "Inner duplicate array id:#{nest_dup[0].object_id}"  # => 60