Returns a cache key that can be used to identify this record.

Product.new.cache_key     # => "products/new"
Product.find(5).cache_key # => "products/5" (updated_at not available)
Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)

You can also pass a list of named timestamps, and the newest in the list will be used to generate the key:

Person.find(5).cache_key(:updated_at, :last_reviewed_at)

# File activerecord/lib/active_record/integration.rb, line 55
def cache_key(*timestamp_names)
  case
  when new_record?
    "#{self.class.model_name.cache_key}/new"
  when timestamp_names.any?
    timestamp = max_updated_column_timestamp(timestamp_names)
    timestamp = timestamp.utc.to_s(cache_timestamp_format)
    "#{self.class.model_name.cache_key}/#{id}-#{timestamp}"
  when timestamp = max_updated_column_timestamp
    timestamp = timestamp.utc.to_s(cache_timestamp_format)
    "#{self.class.model_name.cache_key}/#{id}-#{timestamp}"
  else
    "#{self.class.model_name.cache_key}/#{id}"
  end
end

Returns a String, which Action Pack uses for constructing an URL to this object. The default implementation returns this record's id as a String, or nil if this record's unsaved.

For example, suppose that you have a User model, and that you have a resources :users route. Normally, user_path will construct a path with the user object's 'id' in it:

user = User.find_by(name: 'Phusion')
user_path(user)  # => "/users/1"

You can override to_param in your model to make user_path construct a path using the user's name instead of the user's id:

class User < ActiveRecord::Base
  def to_param  # overridden
    name
  end
end

user = User.find_by(name: 'Phusion')
user_path(user)  # => "/users/Phusion"

# File activerecord/lib/active_record/integration.rb, line 40
def to_param
  # We can't use alias_method here, because method 'id' optimizes itself on the fly.
  id && id.to_s # Be sure to stringify the id for routes
end