self vs instance vs local variables in initialize

self_instance_demo.rb

class UsingSelf
  attr_accessor :a, :b, :c
  def initialize(a, b, c)
    self.a = a
    self.b = b
    self.c = c
  end
end

class UsingInstance
  attr_accessor :a, :b, :c
  def initialize(a, b, c)
    @a = a
    @b = b
    @c = c
  end
end

class UsingLocalVariablesIncorrectly
  attr_accessor :a, :b, :c
  def initialize(a, b, c)
    a = a
    b = b
    c = c
  end
end

using_self = UsingSelf.new('a', 'b', 'c')
puts using_self.a # => 'a'
puts using_self.b # => 'b'
puts using_self.c # => 'c'
using_self.c = 'see'
puts using_self.c # => 'see'

using_instance = UsingInstance.new('a', 'b', 'c')
puts using_instance.a # => 'a'
puts using_instance.b # => 'b'
puts using_instance.c # => 'c'
using_instance.c = 'see'
puts using_instance.c # => 'see'

using_local_variables_incorrectly = UsingLocalVariablesIncorrectly.new('a', 'b', 'c')
puts using_local_variables_incorrectly.a # => nil
puts using_local_variables_incorrectly.b # => nil
puts using_local_variables_incorrectly.c # => nil
using_local_variables_incorrectly.c = 'see'
puts using_local_variables_incorrectly.c # => 'see'