Returns an Enumerable of all key attributes if any is set, regardless if the object is persisted or not. Returns nil if there are no key attributes.

class Person < ActiveRecord::Base
end

person = Person.create
person.to_key # => [1]

# File activemodel/lib/active_model/conversion.rb, line 51
def to_key
  key = respond_to?(:id) && id
  key ? [key] : nil
end

If your object is already designed to implement all of the Active Model you can use the default :to_model implementation, which simply returns self.

class Person
  include ActiveModel::Conversion
end

person = Person.new
person.to_model == person # => true

If your model does not act like an Active Model object, then you should define :to_model yourself returning a proxy object that wraps your object with Active Model compliant methods.

# File activemodel/lib/active_model/conversion.rb, line 39
def to_model
  self
end

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

class Person < ActiveRecord::Base
end

person = Person.create
person.to_param # => "1"

# File activemodel/lib/active_model/conversion.rb, line 64
def to_param
  (persisted? && key = to_key) ? key.join('-') : nil
end

Returns a string identifying the path associated with the object. ActionPack uses this to find a suitable partial to represent the object.

class Person
  include ActiveModel::Conversion
end

person = Person.new
person.to_partial_path # => "people/person"

# File activemodel/lib/active_model/conversion.rb, line 77
def to_partial_path
  self.class._to_partial_path
end