Class: Praxis::MediaType

Inherits:
Blueprint
  • Object
show all
Includes:
Types::MediaTypeCommon
Defined in:
lib/praxis/media_type.rb

Overview

An Internet Media Type as defined in RFC 1590, as used in HTTP (see RFC 2616). As used in the Praxis framework, media types also define the structure and content of entities of that type: the attributes that exist, their names and types.

An object with a media type can be represented on the wire using different structured-syntax encodings; for example, a controller might respond with an actual Widget object, but a Content-Type header specifying ‘application/vnd.acme.widget+json’; Praxis uses the information contained in the media-type definition of Widget to transform the object into an equivalent JSON representation. If the content type ends with ‘+xml’ instead, and the XML handler is registered with the framework, Praxis will respond with an XML representation of the widget. The use of media types allows your application’s models to be decoupled from its HTTP interface specification.

A media type definition consists of:

- a MIME type identifier
- attributes, each of which has a name and a data type
- named links to other resources
- named views, which expose interesting subsets of attributes

Examples:

Declare a widget type that’s used by my supply-chain management app

class MyApp::MediaTypes::Widget < Praxis::MediaType
  description 'Represents a widget'
  identifier 'application/vnd.acme.widget'

  attributes do
    attribute :id, Integer
      description: 'Database ID'
    attribute :href, Attributor::Href,
      description: 'Canonical resource refernece'
    attribute :color, String,
      example: 'red'
    attribute :material, String,
      description: 'Construction medium of the widget',
      values: ['copper', 'steel', 'aluminum']
    attribute :factory, MyApp::MediaTypes::Factory,
      description: 'The factory in which this widget was produced'
  end

  links do
    link :factory,
      description: 'Link to the factory in which this widget was produced'
  end

  # If widgets can be linked-to by other resources, they should have a link view
  view :link do
    attribute :href
  end

  # All resources should have a default view
  view :default do
    attribute :id
    attribute :color
    attribute :material
  end
end

Direct Known Subclasses

MediaTypeCollection

Defined Under Namespace

Classes: DSLCompiler

Class Method Summary collapse

Class Method Details

._finalize! ⇒ Object 



70
71
72
73
74
75
76
77
78
79
80
81
82
 
# File 'lib/praxis/media_type.rb', line 70

def self._finalize!
  super
  if @attribute && self.attributes.key?(:links) && self.attributes[:links].type < Praxis::Links
    # Only define out special links accessor if it was setup using the special DSL
    # (we might have an app defining an attribute called `links` on its own, in which
    # case we leave it be)
    module_eval <<-RUBY, __FILE__, __LINE__ + 1
    def links
      self.class::Links.new(@object)
    end
    RUBY
  end
end

.attributes(opts = {}, &block) ⇒ Object 



66
67
68
 
# File 'lib/praxis/media_type.rb', line 66

def self.attributes(opts={}, &block)
  super(opts.merge(dsl_compiler: MediaType::DSLCompiler), &block)
end