mutate.rb

def spacer
  puts "------------------------------------------------------------------------------------"
end

def blank
  puts ""
end

puts "the string method"
blank

str = 'hello'
puts "string to begin is: #{str}"
puts "string object id is: #{str.object_id}"
blank

def this_no_change(string)
  puts "string object id inside is: #{string.object_id}"
  string += ' world'
  blank
  puts "string inside becomes #{string}"
  puts "string object id inside after is: #{string.object_id}"
  blank
end

this_no_change(str)

puts "string object id after is: #{str.object_id}"
puts "string after is #{str}"

spacer
puts "the array +="

array = ['hello']
puts "array before is #{array}"
puts "array object id is: #{array.object_id}"
puts "array element object id is: #{array[0].object_id}"
blank

def no_change_here(ary)
  puts "array object id inside is: #{ary.object_id}"
  puts "array element object id inside is: #{ary[0].object_id}"
  blank
  ary += ['world']
  puts "array object id inside after is: #{ary.object_id}"
  puts "array element object id inside after is: #{ary[0].object_id}"
  puts "array inside becomes #{ary}"
  blank
end

no_change_here(array)

puts "array afterwards is #{array}"
puts "array object id outside after is: #{array.object_id}"
puts "array element object id outside after is: #{array[0].object_id}"

spacer
puts "your method ary[0] = ary[0] + ' world'"

array = ['hello']
puts "array before is #{array}"
puts "array object id is: #{array.object_id}"
puts "array element object id is: #{array[0].object_id}"
blank

def your_method(ary)
  puts "array object id inside is: #{ary.object_id}"
  puts "array element object id inside is: #{ary[0].object_id}"
  blank
  ary[0] = ary[0] + ' world'
  puts "array object id inside after is: #{ary.object_id}"
  puts "array element object id inside after is: #{ary[0].object_id}"
  puts "array inside becomes #{ary}"
  blank
end

your_method(array)

puts "array afterwards is #{array}"
puts "array object id outside after is: #{array.object_id}"
puts "array element object id outside after is: #{array[0].object_id}"
spacer

def why_does_this(ary)
  puts "array object id inside is: #{ary.object_id}"
  puts "array element object id inside is: #{ary[0].object_id}"
  blank
  ary[0] += ' world'
  puts "array inside is #{ary}"
  puts "array object id inside after is: #{ary.object_id}"
  puts "array element object id inside after is: #{ary[0].object_id}"
  puts "array inside becomes #{ary}"
  blank
end

puts "array before is #{array}"
puts "array object id is: #{array.object_id}"
puts "array element object id is: #{array[0].object_id}"

blank

why_does_this(array)
puts "array afterwards is still...wait what?? #{array}"
puts "array object id outside after is: #{array.object_id}"
puts "array element object id outside after is now!!!: #{array[0].object_id}"