instance_exec vs class_exec

gistfile1.rb

# encoding: utf-8
# different instance_exec whit class_exec

class O
  def self.haha
    puts 'haha'
  end
end

O.instance_exec {
  define_method(:hello) {p 'instance exec method'}  
  puts object_id # => O.object_id
  puts haha # => success
}

O.class_exec {
  define_method(:hello1) {p 'class_exec exec method'}
  puts object_id  # => O.object_id
  puts haha # => success
}

O.new.hello # => success
O.new.hello1 # => success

# reciver both of self, so result is the same on message send.
# instance_exec runtime context is the self's engineclass.
# class_exec runtime context is the self.