module ActiveModel::Conversion

Active Model Conversion

Handles default conversions: #to_model, #to_key, #to_param, and to_partial_path.

Let's take for example this non-persisted object.

class ContactMessage
  include ActiveModel::Conversion

  # ContactMessage are never persisted in the DB
  def persisted?
    false
  end
end

cm = ContactMessage.new
cm.to_model == cm  # => true
cm.to_key          # => nil
cm.to_param        # => nil
cm.to_partial_path # => "contact_messages/contact_message"

Public Instance Methods

to_key() Show source

# File activemodel/lib/active_model/conversion.rb, line 59
def to_key
  key = respond_to?(:id) && id
  key ? [key] : nil
end

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

class Person
  include ActiveModel::Conversion
  attr_accessor :id

  def initialize(id)
    @id = id
  end
end

person = Person.new(1)
person.to_key # => [1]

to_model() Show source

# File activemodel/lib/active_model/conversion.rb, line 41
def to_model
  self
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.

to_param() Show source

# File activemodel/lib/active_model/conversion.rb, line 82
def to_param
  (persisted? && key = to_key) ? key.join("-") : nil
end

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

class Person
  include ActiveModel::Conversion
  attr_accessor :id

  def initialize(id)
    @id = id
  end

  def persisted?
    true
  end
end

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

to_partial_path() Show source

# File activemodel/lib/active_model/conversion.rb, line 95
def to_partial_path
  self.class._to_partial_path
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"