# File activerecord/lib/active_record/integration.rb, line 72
def cache_key
  if new_record?
    "#{model_name.cache_key}/new"
  else
    if cache_version
      "#{model_name.cache_key}/#{id}"
    else
      timestamp = max_updated_column_timestamp

      if timestamp
        timestamp = timestamp.utc.to_formatted_s(cache_timestamp_format)
        "#{model_name.cache_key}/#{id}-#{timestamp}"
      else
        "#{model_name.cache_key}/#{id}"
      end
    end
  end
end

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

Product.new.cache_key     # => "products/new"
Product.find(5).cache_key # => "products/5"

If ActiveRecord::Base.cache_versioning is turned off, as it was in Rails 5.1 and earlier, the cache key will also include a version.

Product.cache_versioning = false
Product.find(5).cache_key  # => "products/5-20071224150000" (updated_at available)

# File activerecord/lib/active_record/integration.rb, line 114
def cache_key_with_version
  if version = cache_version
    "#{cache_key}-#{version}"
  else
    cache_key
  end
end

Returns a cache key along with the version.

# File activerecord/lib/active_record/integration.rb, line 97
def cache_version
  return unless cache_versioning

  if has_attribute?("updated_at")
    timestamp = updated_at_before_type_cast
    if can_use_fast_cache_version?(timestamp)
      raw_timestamp_to_cache_version(timestamp)

    elsif timestamp = updated_at
      timestamp.utc.to_formatted_s(cache_timestamp_format)
    end
  elsif self.class.has_attribute?("updated_at")
    raise ActiveModel::MissingAttributeError, "missing attribute: updated_at"
  end
end

Returns a cache version that can be used together with the cache key to form a recyclable caching scheme. By default, the updated_at column is used for the cache_version, but this method can be overwritten to return something else.

Note, this method will return nil if ActiveRecord::Base.cache_versioning is set to false.

# File activerecord/lib/active_record/integration.rb, line 57
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

Returns a String, which Action Pack uses for constructing a 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"