How do I write a monkey patch for Ruby?

I am usi开发者_如何学Cng Rails 3 and getting an error that looks like this:

undefined method `persisted?' for []:Array

I want to monkeypatch to fix this problem. First of all: what is it supposed to look like? I know very little about the nesting of the Array class in Ruby's source code. I'd appreciate the guidance.

---

basically you just write the class and function like you would for any other class and it gets added to the original class definition.

Like So:

class Array
    def persisted?
        # Does it persist?
    end
end

---

Monkey-patching looks like this:

# patches/array.rb
class Array # Array is a top-level class
  def persisted?
    false # or your own implementation
  end
end

# some/other/script.rb
require 'path/to/patches/array.rb'
my_array = [1, 2, 3]
puts my_array.persisted?

Now: what can you possibly mean by asking an Array instance whether it is persisted?