I have the following code:
#!/usr/bin/ruby
class Person
def self.speak
p = self.new
puts "Hello"
p.chatter
end
private
def chatter
puts "Chattering"
end
end
p = Person.new
Person.speak
I'd like to make chatter private, accessible only within p.. but I want p to be able to access it within the class method. Is there a better way to design this so chatter isn't available to the public, but a "factory" method like self.speak can call chatter?
In Ruby 1.8.7, "send" bypasses the usual protections against calling private methods:
#!/usr/bin/ruby1.8
class Person
def self.speak
puts "Hello"
new.send(:chatter)
end
def speak
puts "Hello"
puts chatter
end
private
def chatter
puts "Chattering"
end
end
Person.speak # => Hello
# => Chattering
Person.new.speak # => Hello
# => Chattering
However, what you want can be achieved without any voodoo, by simply having the class method do all the work, and the instance method defer to the class method:
class Person
def self.speak
puts "Hello"
puts "Chatter"
end
def speak
self.class.speak
end
end
If you had more than a few of these forwarding methods, it might be convenient to make a helper method that makes them for you:
module DelegateToClass
def delegate_to_class(name)
define_method(name) do |*args|
self.class.send(name, *args)
end
end
end
class Person
extend DelegateToClass
def self.speak
puts "Hello"
puts "Chatter"
end
delegate_to_class :speak
end
The built-in module Forwardable can do this just as well:
require 'forwardable'
class Person
extend Forwardable
def self.speak
puts "Hello"
puts "Chatter"
end
def_delegator self, :speak
end
def_delegator also bypasses protections against private methods.
There's a number of ways to do this. One approach would be a class method which instantiates a new instance and calls the #speak method on the instance.
class Person
def self.speak
new.speak
end
def speak
puts "Hello"
chatter
end
private
def chatter
puts "Chattering"
end
end
Then you could call it in either the class or instance context:
p = Person.new
p.speak
# ...or...
Person.speak
