module ActiveModel::Conversion

person.to_param # => "1"
person = Person.new(1)

end
end
true
def persisted?

end
@id = id
def initialize(id)

attr_accessor :id
include ActiveModel::Conversion
class Person

or +nil+ if persisted? is +false+.
Returns a +string+ representing the object's key suitable for use in URLs,

def to_param
  (persisted? && key = to_key) ? key.join("-") : nil
end