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API Documentation Tool Join the chat at Latest release

Apipie-rails is a DSL and Rails engine for documenting your RESTful API. Instead of traditional use of #comments, Apipie lets you describe the code, through the code. This brings advantages like:

  • No need to learn yet another syntax, you already know Ruby, right?
  • Possibility of reusing the docs for other purposes (such as validation)
  • Easier to extend and maintain (no string parsing involved)
  • Possibility of reusing other sources for documentation purposes (such as routes etc.)

The documentation is available from within your app (by default under the /apipie path.) In development mode, you can see the changes as you go. It's markup language agnostic, and even provides an API for reusing the documentation data in JSON.

Getting started

The easiest way to get Apipie up and running with your app is:

echo "gem 'apipie-rails'" >> Gemfile
bundle install
rails g apipie:install

Now you can start documenting your resources and actions (see DSL Reference for more info):

api :GET, '/users/:id'
param :id, :number
def show
  # ...

Run your application and see the result at http://localhost:3000/apipie. For further processing, you can use http://localhost:3000/apipie.json.

For a more comprehensive getting started guide, see this demo, which includes features such as generating documentation from tests, recording examples etc.



Pajk and iNecas


See Contributors page. Special thanks to all of them!


Apipie-rails is released under the MIT License


DSL Reference

Resource Description

You can describe a resource on the controller level. The description is introduced by calling resource_description do ... end.

Inheritance is supported, so you can specify common params for group of controllers in their parent class.

The following keywords are available (all are optional):

How the resource will be referenced in Apipie (paths, see command etc.); by default controller_name.downcase is used.
Human readable name of resource. By default is used.
short (also short_description)
Short description of the resource (it's shown on both the list of resources, and resource details)
desc (also description and full_description)
Full description of the resource (shown only in resource details)
Common params for all methods defined in controller/child controllers.
Common responses for all methods defined in controller/child controllers.
What URL is the resource available under.
api_versions (also api_version)
What versions does the controller define the resource. (See Versioning for details.)
Request / response formats.
Describe every possible error that can happen when calling all methods defined in controller. HTTP response code and description can be provided.
In case of versioning, this sets app info description on a per_version basis.
Hash or array with custom metadata.
Boolean value indicating if the resource is marked as deprecated. (Default false)


resource_description do
  short 'Site members'
  formats ['json']
  param :id, Fixnum, :desc => "User ID", :required => false
  param :resource_param, Hash, :desc => 'Param description for all methods' do
    param :ausername, String, :desc => "Username for login", :required => true
    param :apassword, String, :desc => "Password for login", :required => true
  api_version "development"
  error 404, "Missing"
  error 500, "Server crashed for some <%= reason %>", :meta => {:anything => "you can think of"}
  error :unprocessable_entity, "Could not save the entity."
  returns :code => 403 do
     property :reason, String, :desc => "Why this was forbidden"
  meta :author => {:name => 'John', :surname => 'Doe'}
  deprecated false
  description <<-EOS
    == Long description
     Example resource for rest api documentation
     These can now be accessed in <tt>shared/header</tt> with:
       Headline: <%= headline %>
       First name: <%= person.first_name %>

     If you need to find out whether a certain local variable has been
     assigned a value in a particular render call, you need to use the
     following pattern:

     <% if local_assigns.has_key? :headline %>
        Headline: <%= headline %>
     <% end %>

    Testing using <tt>defined? headline</tt> will not work. This is an
    implementation restriction.

    === Template caching

    By default, Rails will compile each template to a method in order
    to render it. When you alter a template, Rails will check the
    file's modification time and recompile it in development mode.

Method Description

Then describe methods available to your API.


Describe how this method is exposed, and provide a short description. The first parameter is HTTP method (one of :GET/:POST/:PUT/:DELETE). The second parameter is the relative URL path which is mapped to this method. The last parameter is the methods short description. You can use this +api+ method more than once per method. It could be useful when there are more routes mapped to it.

When providing just one argument (description), or no argument at all, the paths will be loaded from the routes.rb file.

Provide a short description and additional option. The last parameter is the methods short description. The paths will be loaded from routes.rb file. See Rails Routes Integration for more details.
api_versions (also api_version)
What version(s) does the action belong to. (See Versioning for details.)
Look at Parameter description section for details.
Look at Response description section for details.
Method level request / response formats.
Describe each possible error that can happen while calling this method. HTTP response code and description can be provided.
Full method description, which will be converted into HTML by the chosen markup language processor.
Provide an example of the server response; whole communication or response type. It will be formatted as code.
Provide reference to another method, this has to be a string with controller_name#method_name.
Hash or array with custom metadata.
Resource is hidden from documentation when set to false (true by default)


# The simplest case: just load the paths from routes.rb
def index

# More complex example
api :GET, "/users/:id", "Show user profile"
show false
error :code => 401, :desc => "Unauthorized"
error :code => 404, :desc => "Not Found", :meta => {:anything => "you can think of"}
param :session, String, :desc => "user is logged in", :required => true
param :regexp_param, /^[0-9]* years/, :desc => "regexp param"
param :array_param, [100, "one", "two", 1, 2], :desc => "array validator"
param :boolean_param, [true, false], :desc => "array validator with boolean"
param :proc_param, lambda { |val|
  val == "param value" ? true : "The only good value is 'param value'."
}, :desc => "proc validator"
param :param_with_metadata, String, :desc => "", :meta => [:your, :custom, :metadata]
returns :code => 200, :desc => "a successful response" do
   property :value1, String, :desc => "A string value"
   property :value2, Integer, :desc => "An integer value"
   property :value3, Hash, :desc => "An object" do
     property :enum1, ['v1', 'v2'], :desc => "One of 2 possible string values"
description "method description"
formats ['json', 'jsonp', 'xml']
meta :message => "Some very important info"
example " 'user': {...} "
see "users#showme", "link description"
see :link => "users#update", :desc => "another link description"
def show

Parameter Description

Use param to describe every possible parameter. You can use the Hash validator in conjunction with a block given to the param method to describe nested parameters.

The first argument is the parameter name as a symbol.
Second parameter is the parameter validator, choose one from section Validators
Parameter description.
Set this true/false to make it required/optional. Default is optional
Setting this to true means that nil can be passed.
Like allow_nil, but for blank values. false, "", ' ', nil, [], and {} are all blank.
Used by the processing functionality to change the name of a key params.
Hash or array with custom metadata.
Parameter is hidden from documentation when set to false (true by default)
Specify the message to be returned if the parameter is missing as a string or Proc. Defaults to Missing parameter #{name} if not specified.
This can be set to :request or :response. Setting to :response causes the param to be ignored when used as part of a request description. Setting to :request causes this param to be ignored when used as part of a response description. If only_in is not specified, the param definition is used for both requests and responses. (Note that the keyword property is similar to param, but it has a :only_in => :response default).


param :user, Hash, :desc => "User info" do
  param :username, String, :desc => "Username for login", :required => true
  param :password, String, :desc => "Password for login", :required => true
  param :membership, ["standard","premium"], :desc => "User membership"
  param :admin_override, String, :desc => "Not shown in documentation", :show => false
  param :ip_address, String, :desc => "IP address", :required => true, :missing_message => lambda { I18n.t("ip_address.required") }
def create

DRY with param_group

Often, params occur together in more actions. Typically, most of the params for create and update actions are shared between them.

These params can be extracted with def_param_group and param_group keywords.

The definition is looked up in the scope of the controller. If the group is defined in a different controller, it might be referenced by specifying the second argument.


# v1/users_controller.rb
def_param_group :address do
  param :street, String
  param :number, Integer
  param :zip, String

def_param_group :user do
  param :user, Hash do
    param :name, String, "Name of the user"
    param_group :address

api :POST, "/users", "Create an user"
param_group :user
def create
  # ...

api :PUT, "/users/:id", "Update an user"
param_group :user
def update
  # ...

# v2/users_controller.rb
api :POST, "/users", "Create an user"
param_group :user, V1::UsersController
def create
  # ...

Action Aware params

In CRUD operations, this pattern occurs quite often - params that need to be set are:

  • for create action: required => true and allow_nil => false
  • for update action: required => false and allow_nil => false

This makes it hard to share the param definitions across theses actions. Therefore, you can make the description a bit smarter by setting :action_aware => true.

You can specify explicitly how the param group should be evaluated with :as option (either :create or :update)


def_param_group :user do
  param :user, Hash, :action_aware => true do
    param :name, String, :required => true
    param :description, String

api :POST, "/users", "Create an user"
param_group :user
def create
  # ...

api :PUT, "/users/admin", "Create an admin"
param_group :user, :as => :create
def create_admin
  # ...

api :PUT, "/users/:id", "Update an user"
param_group :user
def update
  # ...

In this case, user[name] will be not be allowed nil for all actions and required only for create and create_admin. Params with allow_nil set explicitly don't have this value changed.

Action awareness is inherited from ancestors (in terms of nested params).

Response Description

The response from an API call can be documented by adding a returns statement to the method description. This is especially useful when using Apipie to auto-generate a machine-readable Swagger definition of your API (see the swagger section for more details).

A returns statement has several possible formats:

# format #1:  reference to a param-group
returns <param-group-name> [, :code => <number>|<http-response-code-symbol>] [, :desc => <human-readable description>]

# format #2:  inline response definition
returns :code => <number>|<http-response-code-symbol> [, :desc => <human-readable description>] do
    # property ...
    # property ...
    # param_group ...

# format #3:  describing an array-of-objects response
returns :array_of => <param-group-name> [, :code => <number>|<http-response-code-symbol>] [, :desc => <human-readable description>]

If the :code argument is ommitted, 200 is used.


# ------------------------------------------------
# Example of format #1 (reference to param-group):
# ------------------------------------------------
# the param_group :pet is defined here to describe the output returned by the method below.
def_param_group :pet do
  property :pet_name, String, :desc => "Name of pet"
  property :animal_type, ['dog','cat','iguana','kangaroo'], :desc => "Type of pet"

api :GET, "/pets/:id", "Get a pet record"
returns :pet, :desc => "The pet"
def show_detailed
  render JSON({:pet_name => "Skippie", :animal_type => "kangaroo"})

# ------------------------------------------------
# Example of format #2 (inline):
# ------------------------------------------------
api :GET, "/pets/:id/with-extra-details", "Get a detailed pet record"
returns :code => 200, :desc => "Detailed info about the pet" do
  param_group :pet
  property :num_legs, Integer, :desc => "How many legs the pet has"
def show
  render JSON({:pet_name => "Barkie", :animal_type => "iguana", :legs => 4})

# ------------------------------------------------
# Example of format #3 (array response):
# ------------------------------------------------
api :GET, "/pets", "Get all pet records"
returns :array_of => :pet, :code => 200, :desc => "All pets"
def index
  render JSON([ {:pet_name => "Skippie", :animal_type => "kangaroo"},
                {:pet_name => "Woofie", :animal_type => "cat"} ])

Note the use of the property keyword rather than param. This is the preferred mechanism for documenting response-only fields.

The Property keyword

property is very similar to param with the following differences:

  • a property is :only_in => :response by default
  • a property is :required => :true by default
  • a property can be an :array_of objects
property :example, :array_of => Hash do
  property :number1, Integer
  property :number2, Integer
Describing multiple return codes

To describe multiple possible return codes, the :returns keyword can be repeated as many times as necessary (once for each return code). Each one of the :returns entries can specify a different response format.

api :GET, "/pets/:id/extra_info", "Get extra information about a pet"
  returns :desc => "Found a pet" do
    param_group :pet
    property 'pet_history', Hash do
      param_group :pet_history
  returns :code => :unprocessable_entity, :desc => "Fleas were discovered on the pet" do
    param_group :pet
    property :num_fleas, Integer, :desc => "Number of fleas on this pet"
  def show_extra_info
    # ... implementation here
Reusing a param_group to describe inputs and outputs

In many cases (such as CRUD implementations), the output from certain API calls is very similar - but not identical - to the inputs of the same or other API calls.

If you already have a :param_group that defines the input to a create or update routine, it would be quite frustrating to have to define a completely separate :param_group to describe the output of the show routine.

To address such situations, it is possible to define a single :param_group which combines param and property statements (as well as :only_in => :request / :only_in => :response) to differentiate between fields that are only expected in the request, only included in the response, or common to both.

This is somewhat analogous to the way Action Aware params work.

 def_param_group :user_record
     param :name, String                                         # this is commong to both the request and the response
     param :force_update, [true, false], :only_in => :request    # this does not show up in responses
     property :last_login, String                                # this shows up only in the response

api :POST, "/users", "Create a user"
param_group :user_record  # the :last_login field is not expected here, but :force_update is
def create
  # ...

api :GET, "/users", "Create a user"
returns :array_of => :user_record  # the :last_login field will be included in the response, but :force_update will not
def index
  # ...
Embedded response descriptions

If the code creating JSON responses is encapsulated within dedicated classes, it can be more convenient to place the response descriptions outside of the controller and embed them within the response generator.

To support such use cases, Apipie allows any class to provide a describe_own_properties class method which returns a description of the properties such a class would expose. It is then possible to specify that class in the returns statement instead of a param_group.

The describe_own_properties method is expected to return an array of Apipie::prop objects, each one describing a single property.

class Pet
  # this method is automatically called by Apipie when Pet is specified as the returned object type
  def self.describe_own_properties
        Apipie::prop(:pet_name, 'string', {:description => 'Name of pet', :required => false}),
        Apipie::prop(:animal_type, 'string', {:description => 'Type of pet', :values => ["dog", "cat", "iguana", "kangaroo"]}),
        Apipie::additional_properties(false)  # this indicates that :pet_name and :animal_type are the only properties in the response

  # this method w
  def json
    JSON({:pet_name => @name, :animal_type => @type })

class PetsController
    api :GET, "/index", "Get all pets"
    returns :array_of => Pet  # Pet is a 'self-describing-class'
    def index
     # ...

A use case where this is very useful is when JSON generation is done using a reflection mechanism or some other sort of declarative mechanism.

The Apipie::prop function expects the following inputs:

Apipie::prop(<property-name>, <property-type>, <options-hash> [, <array of sub-properties>])

# property-name should be a symbol
# property-type can be any of the following strings:
#   "integer": maps to a swagger "integer" with an "int32" format
#   "long": maps to a swagger "integer" with an "int64" format
#   "number": maps to a swagger "number"(no format specifier)
#   "float": maps to a swagger "number" with a "float" format
#   "double": maps to a swagger "number" with a "double" format
#   "string": maps to a swagger "string" (no format specifier)
#   "byte": maps to a swagger "string" with a "byte" format
#   "binary": maps to a swagger "string" with a "binary" format
#   "boolean": maps to a swagger "boolean" (no format specifier)
#   "date": maps to a swagger "string" with a "date" format
#   "dateTime": maps to a swagger "string" with a "date-time" format
#   "password": maps to a swagger "string" with a "password" format
#   "object": the property has sub-properties. include <array of sub-properties> in the call.
# (see for more information
# about the mapped swagger types)
# options-hash can include any of the options fields allowed in a :returns statement.
# additionally, it can include the ':is_array => true', in which case the property is understood to be
# an array of the described type.

To describe an embedded object:

# PetWithMeasurements is a self-describing class with an embedded object
class PetWithMeasurements
  def self.describe_own_properties
        Apipie::prop(:pet_name, 'string', {:description => 'Name of pet', :required => false}),
        Apipie::prop('animal_type', 'string', {:description => 'Type of pet', :values => ["dog", "cat", "iguana", "kangaroo"]}),
        Apipie::prop(:pet_measurements, 'object', {}, [
            Apipie::prop(:weight, 'number', {:description => "Weight in pounds" }),
            Apipie::prop(:height, 'number', {:description => "Height in inches" }),
            Apipie::prop(:num_legs, 'number', {:description => "Number of legs", :required => false }),

# PetWithManyMeasurements is a self-describing class with an embedded array of objects
class PetWithManyMeasurements
  def self.describe_own_properties
        Apipie::prop(:pet_name, 'string', {:description => 'Name of pet', :required => false}),
        Apipie::prop(:many_pet_measurements, 'object', {is_array: true}, [
            Apipie::prop(:weight, 'number', {:description => "Weight in pounds" }),
            Apipie::prop(:height, 'number', {:description => "Height in inches" }),


Sometimes, the actions are not defined in the controller class directly but included from a module instead. You can load the Apipie DSL into the module by extending it with Apipie::DSL::Concern.

The module can be used in more controllers. Therefore there is a way to substitute parts of the documentation in the module with controller specific values. These substitutions can be stated explicitly with apipie_concern_subst(:key => "value") (needs to be called before the module is included to take effect). The substitutions are performed in the paths and descriptions of APIs and names and descriptions of params.

There are some default substitutions available:

value of controller.controller_path, e.g. api/users for Api::UsersController. Only if not using the api! keyword.
Apipie identifier of the resource, e.g. users for Api::UsersController or set by resource_id


# users_module.rb
module UsersModule
  extend Apipie::DSL::Concern

  api :GET, '/:controller_path', 'List :resource_id'
  def index
    # ...

  api! 'Show a :resource'
  def show
    # ...

  api :POST, '/:resource_id', "Create a :resource"
  param :concern, Hash, :required => true
    param :name, String, 'Name of a :resource'
    param :resource_type, ['standard','vip']
  def create
    # ...

  api :GET, '/:resource_id/:custom_subst'
  def custom
    # ...

# users_controller.rb
class UsersController < ApplicationController

  resource_description { resource_id 'customers' }

  apipie_concern_subst(:custom_subst => 'custom', :resource => 'customer')
  include UsersModule

  # the following paths are documented
  # api :GET, '/users'
  # api :GET, '/customers/:id', 'Show a customer'
  # api :POST, '/customers', 'Create a customer'
  #   param :customer, :required => true do
  #     param :name, String, 'Name of a customer'
  #     param :customer_type, ['standard', 'vip']
  #   end
  # api :GET, '/customers/:custom'

Sometimes, it's needed to extend an existing controller method with additional parameters (usually when extending exiting API from plugins/rails engines). The concern can be also used for this purposed, using update_api method. The params defined in this block are merged with the params of the original method in the controller this concern is included to.


module Concerns
  module OauthConcern
    extend Apipie::DSL::Concern

    update_api(:create, :update) do
      param :user, Hash do
        param :oauth, String, :desc => 'oauth param'

The concern needs to be included to the controller after the methods are defined (either at the end of the class, or by using Controller.send(:include, Concerns::OauthConcern).

Response validation

The swagger definitions created by Apipie can be used to auto-generate clients that access the described APIs. Those clients will break if the responses returned from the API do not match the declarations. As such, it is very important to include unit tests that validate the actual responses against the swagger definitions.

The implemented mechanism provides two ways to include such validations in RSpec unit tests: manual (using an RSpec matcher) and automated (by injecting a test into the http operations 'get', 'post', raising an error if there is no match).

Example of the manual mechanism:

require 'apipie/rspec/response_validation_helper'

RSpec.describe MyController, :type => :controller, :show_in_doc => true do

  describe "GET stuff with response validation" do
    render_views   # this makes sure the 'get' operation will actually
                   # return the rendered view even though this is a Controller spec

    it "does something" do
      response = get :index, {format: :json}

      # the following expectation will fail if the returned object
      # does not match the 'returns' declaration in the Controller,
      # or if there is no 'returns' declaration for the returned
      # HTTP status code
      expect(response).to match_declared_responses

Example of the automated mechanism:

require 'apipie/rspec/response_validation_helper'

RSpec.describe MyController, :type => :controller, :show_in_doc => true do

  describe "GET stuff with response validation" do

    it "does something" do
      get :index, {format: :json}
    it "does something else" do
      get :another_index, {format: :json}

  describe "GET stuff without response validation" do
    it "does something" do
      get :index, {format: :json}
    it "does something else" do
      get :another_index, {format: :json}

Configuration Reference

Create a configuration file in e.g. /config/initializers/apipie.rb. You can set the application name, footer text, API and documentation base URL and turn off validations. You can also choose your favorite markup language for full descriptions.

Name of your application; used in breadcrumbs navigation.
Copyright information (shown in page footer).
If true recorded examples are compressed using Zlib. Useful for big test-suits.
Documentation frontend base url.
Base url for default version of your API. To set it for specific version use config.api_base_url[version] = url.
Default API version to be used (1.0 by default)
Parameters validation is turned off when set to false. When set to :explicitly, you must invoke parameter validation yourself by calling controller method apipie_validations (typically in a before_action). When set to :implicitly (or just true), your controller's action methods are wrapped with generated methods which call apipie_validations, and then call the action method. (:implicitly by default)
Check the value of params against specified validators (true by default)
Check the params presence against the documentation.
Check the received params to ensure they are defined in the API. (false by default)
Process and extract the parameter defined from the params of the request to the api_params variable
Application long description.
Set to enable/disable reloading controllers (and the documentation with it). Enabled by default in development.
For reloading to work properly you need to specify where your API controllers are. Can be an array if multiple paths are needed
Set if your application uses a custom API router, different from the Rails default
An object providing the translation from the Rails routes to the format usable in the documentation when using the api! keyword. By default, the Apipie::RoutesFormatter is used.
You can choose markup language for descriptions of your application, resources and methods. RDoc is the default but you can choose from or In order to use Markdown you need Maruku gem and for Textile you need RedCloth. Add those to your gemfile and run bundle if you want to use them. You can also add any other markup language processor.
Name of a layout template to use instead of Apipie's layout. You can use Apipie.include_stylesheets and Apipie.include_javascripts helpers to include Apipie's stylesheets and javascripts.
An array of controller names (strings) (might include actions as well) to be ignored when generationg the documentation e.g. %w[Api::CommentsController Api::PostsController#post]
Use controller paths instead of controller names as resource id. This prevents same named controllers overwriting each other.
Pass a proc in order to authenticate user. Pass nil for no authentication (by default).
Pass a proc in order to authorize controllers and methods. The Proc is evaluated in the controller context.
Set this to true to set show_in_doc=1 in all recorded examples
The extension to use for API pages ('.html' by default). Link extensions in static API docs cannot be changed from '.html'.
List of languages the API documentation should be translated into. Empty by default.
Locale used for generating documentation when no specific locale is set. Set to 'en' by default.
Pass locale setter/getter
config.locale = lambda { |loc| loc ? FastGettext.set_locale(loc) : FastGettext.locale }
Pass proc to translate strings using the localization library your project uses. For example see Localization


Apipie.configure do |config|
  config.app_name = "Test app"
  config.copyright = "&copy; 2012 Pavel Pokorny"
  config.doc_base_url = "/apidoc"
  config.api_base_url = "/api"
  config.validate = false
  config.markup =
  config.reload_controllers = Rails.env.development?
  config.api_controllers_matcher = File.join(Rails.root, "app", "controllers", "**","*.rb")
  config.api_routes = Rails.application.routes
  config.app_info["1.0"] = "
    This is where you can inform user about your application and API
    in general.
  config.authenticate = do
     authenticate_or_request_with_http_basic do |username, password|
       username == "test" && password == "supersecretpassword"
  config.authorize = do |controller, method, doc|
    !method   # show all controller doc, but no method docs.
Used in ChecksumInHeaders middleware (see JSON checksums for more info). It contains path prefix(es) where the header with checksum is added. If set to nil, checksum is added in headers in every response. e.g. %w[/api /apipie]
If set to true, the checksum is recalculated with every documentation_reload call

Rails Routes Integration

Apipie is able to load the information about the paths based on the routes defined in the Rails application, by using the api! keyword in the DSL.

It should be usable out of box, however, one might want to do some customization (such as omitting some implicit parameters in the path etc.). For this kind of customizations one can create a new formatter and pass as the Apipie.configuration.routes_formatter option, like this:

class MyFormatter < Apipie::RoutesFormatter
  def format_path(route)
    super.gsub(/\(.*?\)/, '').gsub('//','') # hide all implicit parameters

Apipie.configure do |config|
 config.routes_formatter =

A similar way can be used to influence things like order, or a description of the loaded APIs, even omitting some paths if needed.


The goal is to extract and pre-process parameters of the request.

For example Rails, by default, transforms an empty array to nil value. Perhaps you want to transform it again into an empty array. Or you want to support an enumeration type (comma separated values) and you want to automatically transform this string into an array.

To use it, set the process_params configuration variable to true.

Also by using as you can separate your API parameter names from the names you are using inside your code.

To implement it, you just have to write a process_value function in your validator:

For an enumeration type:

def process_value(value)
 value ? value.split(',') : []


Every parameter needs to have an associated validator. For now there are some basic validators. You can always provide your own to achieve complex results.

If validations are enabled (default state) the parameters of every request are validated. If the value is wrong an +ArgumentError+ exception is raised and can be rescued and processed. It contains a description of the parameter value expectations. Validations can be turned off in the configuration file.

Parameter validation normally happens after before_actions, just before your controller method is invoked. If you prefer to control when parameter validation occurs, set the configuration parameter validate to :explicitly. You must then call the apipie_validations method yourself, e.g.:

before_action: :apipie_validations

This is useful if you have before_actions which use parameter values: just add them after the apipie_validations before_action.


Check the parameter type. Only String, Hash and Array are supported for the sake of simplicity. Read more to find out how to add your own validator.

param :session, String, :desc => "user is logged in", :required => true
param :facts, Hash, :desc => "Additional optional facts about the user"


Check parameter value against given regular expression.

param :regexp_param, /^[0-9]* years/, :desc => "regexp param"


Check if parameter value is included in the given array.

param :enum_param, [100, "one", "two", 1, 2], :desc => "enum validator"


If you need more complex validation and you know you won't reuse it, you can use the Proc/lambda validator. Provide your own Proc, taking the value of the parameter as the only argument. Return true if value passes validation or return some text about what is wrong otherwise. _Don't use the keyword return if you provide an instance of Proc (with lambda it is ok), just use the last statement return property of ruby.

param :proc_param, lambda { |val|
  val == "param value" ? true : "The only good value is 'param value'."
}, :desc => "proc validator"


You can describe hash parameters in depth if you provide a block with a description of nested values.

param :user, Hash, :desc => "User info" do
  param :username, String, :desc => "Username for login", :required => true
  param :password, String, :desc => "Password for login", :required => true
  param :membership, ["standard","premium"], :desc => "User membership"


In fact there isn't any NilValidator, but setting it to nil can be used to override parameters described on the resource level.

param :user, nil
def destroy


Check if the parameter is an array


Check if the parameter is a decimal number

param :latitude, :decimal, :desc => "Geographic latitude", :required => true
param :longitude, :decimal, :desc => "Geographic longitude", :required => true

Additional options

Specify the type of items. If not given it accepts an array of any item type
Specify an array of valid item values.


Assert things is an array of any items

param :things, Array

Assert hits must be an array of integer values

param :hits, Array, of: Integer

Assert colors must be an array of valid string values

param :colors, Array, in: ["red", "green", "blue"]

The retrieving of valid items can be deferred until needed using a lambda. It is evaluated only once

param :colors, Array, in: ->  { Color.all.pluck(:name) }


You can describe nested parameters in depth if you provide a block with a description of nested values.

param :comments, Array, :desc => "User comments" do
  param :name, String, :desc => "Name of the comment", :required => true
  param :comment, String, :desc => "Full comment", :required => true

Adding custom validator

Only basic validators are included but it is really easy to add your own. Create a new initializer with a subclass of Apipie::Validator::BaseValidator. Two methods are required to implement this - instance method validate(value) and class method build(param_description, argument, options, block).

When searching for the validator +build+ method, every subclass of Apipie::Validator::BaseValidator is called. The first one that returns the constructed validator object is used.

Example: Adding IntegerValidator

We want to check if the parameter value is an integer like this:

param :id, Integer, :desc => "Company ID"

So we create apipie_validators.rb initializer with this content:

class IntegerValidator < Apipie::Validator::BaseValidator

  def initialize(param_description, argument)
    @type = argument

  def validate(value)
    return false if value.nil?
    !!(value.to_s =~ /^[-+]?[0-9]+$/)

  def, argument, options, block)
    if argument == Integer || argument == Fixnum, argument)

  def description
    "Must be #{@type}."

Parameters of the build method:

Instance of Apipie::ParamDescription contains all given information about the validated parameter.
Specified validator; in our example it is +Integer+
Hash with specified options, for us just {:desc => "Company ID"}
Block converted into Proc, use it as you desire. In this example nil.


Every resource/method can belong to one or more versions. The version is specified with the api_version DSL keyword. When not specified, the resource belongs to config.default_version ("1.0" by default)

resource_description do
  api_versions "1", "2"

api :GET, "/api/users/", "List: users"
api_version "1"
def index
  # ...

api :GET, "/api/users/", "List: users", :deprecated => true

In the example above we say the whole controller/resource is defined for versions "1" and "2", but we override this by explicitly saying index belongs only to version "1". Also, inheritance works (therefore we can specify the api_version for the parent controller, and all children will know about that). Routes can be flagged as deprecated, and an annotation will be added to them when viewing in the API documentation.

From the Apipie API perspective, the resources belong to the version. With versioning, there are paths like this provided by apipie:


When not specifying the version explicitly in the path (or in DSL), default version (Apipie.configuration.default_version) is used instead ("1.0" by default). Therefore, an application that doesn't need versioning should work as before.

The static page generator takes a version parameter (or uses default).

You can specify the versions for the examples, with the versions keyword. It specifies the versions the example is used for. When not specified, it's shown in all versions with the given method.

When referencing or quering the resource/method descripion, this format should be used: "version#resource#method". When not specified, the default version is used instead.


The default markup language is RDoc. It can be changed in the config file (config.markup=) to one of these:

Use You need Maruku gem.
Use You need RedCloth gem.

Or provide you own object with a to_html(text) method. For inspiration, this is how Textile markup usage is implemented:

class Textile
  def initialize
    require 'RedCloth'
  def to_html(text)


Apipie has support for localized API documentation in both formats (JSON and HTML). Apipie uses the library I18n for localization of itself. Check config/locales directory for available translations.

A major part of strings in the documentation comes from the API. As preferences regarding localization libraries differ amongst project, Apipie needs to know how to set the locale for your project, and how to translate a string using the library your project uses. That can be done using lambdas in configuration.

Sample configuration when your project uses FastGettext

Apipie.configure do |config|
 config.languages = ['en', 'cs']
 config.default_locale = 'en'
 config.locale = lambda { |loc| loc ? FastGettext.set_locale(loc) : FastGettext.locale }
 config.translate = lambda do |str, loc|
   old_loc = FastGettext.locale
   trans = _(str)

And the strings in the API documentation need to be marked with the N_() function

api :GET, "/users/:id", N_("Show user profile")
param :session, String, :desc => N_("user is logged in"), :required => true

When your project use I18n, localization related configuration could appear as follows

Apipie.configure do |config|
 config.languages = ['en', 'cs']
 config.default_locale = 'en'
 config.locale = lambda { |loc| loc ? I18n.locale = loc : I18n.locale }
 config.translate = lambda do |str, loc|
   return '' if str.blank?
   I18n.t str, locale: loc, scope: 'doc'

And the strings in the API documentation needs to be in the form of translation keys

api :GET, "/users/:id", "show_user_profile"
param :session, String, :desc => "user_is_logged_in", :required => true

The localized versions of the documentation are distinguished by language in the filename. E.g. doc/apidoc/apidoc.cs.html is static documentation in the Czech language. If the language is missing, e.g. doc/apidoc/apidoc.html, the documentation is localized with the default_locale.

The dynamic documentation follows the same schema. The http://localhost:3000/apidoc/v1.cs.html is documentation for version '1' of the API in the Czech language. For JSON descriptions, the API applies the same format: http://localhost:3000/apidoc/v1.cs.json

Modifying Views

To modify the views of your documentation, run rails g apipie:views. This will copy the Apipie views to app/views/apipie/apipies and app/views/layouts/apipie.

Static files

To generate a static version of documentation (perhaps to put it on your project site or something), run the rake apipie:static task. It will create a set of HTML files (multi-pages, single-page, plain) in your doc directory. If you prefer a JSON version run rake apipie:static_json. By default the documentation for the default API version is used. You can specify the version with rake apipie:static[2.0]

When you want to avoid any unnecessary computation in production mode, you can generate a cache with rake apipie:cache and configure the app to use it in production with config.use_cache = Rails.env.production?

Default cache dir is File.join(Rails.root, "public", "apipie-cache"), you can change it to where you want, example: config.cache_dir = File.join(Rails.root, "doc", "apidoc").

If, for some complex cases, you need to generate/re-generate just part of the cache use rake apipie:cache cache_part=index resp. rake apipie:cache cache_part=resources To generate it for different locations for further processing use rake apipie:cache OUT=/tmp/apipie_cache.

Static Swagger (OpenAPI 2.0) files

To generate a static Swagger definition file from the api, run rake apipie:static_swagger_json. By default the documentation for the default API version is used. You can specify the version with rake apipie:static_swagger_json[2.0]. A swagger file will be generated for each locale. The files will be generated in the same location as the static_json files, but instead of being named schema_apipie[.locale].json, they will be called schema_swagger[.locale].json.

Specifying default values for parameters

Swagger allows method definitions to include an indication of the the default value for each parameter. To include such indications, use :default_value => <some value> in the parameter definition DSL. For example:

param :do_something, Boolean, :desc => "take an action", :required => false, :default_value => false

Generated Warnings

The help identify potential improvements to your documentation, the swagger generation process issues warnings if it identifies various shortcomings of the DSL documentation. Each warning has a code to allow selective suppression (see swagger-specific configuration below)

100:missing short description for method
101:added missing / at beginning of path
102:no return codes specified for method
103:a parameter is a generic Hash without an internal type specification
104:a parameter is an 'in-path' parameter, but specified as 'not required' in the DSL
105:a parameter is optional but does not have a default value specified
106:a parameter was ommitted from the swagger output because it is a Hash without fields in a formData specification
107:a path parameter is not described
108:inferring that a parameter type is boolean because described as an enum with [false,true] values

Swagger-Specific Configuration Parameters

There are several configuration parameters that determine the structure of the generated swagger file:


If the value is :form_data - the swagger file will indicate that the server consumes the content types application/x-www-form-urlencoded and multipart/form-data. Non-path parameters will have the value "in": "formData". Note that parameters of type Hash that do not have any fields in them will be ommitted from the resulting files, as there is no way to describe them in swagger.

If the value is :json - the swagger file will indicate that the server consumes the content type application/json. All non-path parameters will be included in the schema of a single "in": "body" parameter of type object.

You can specify the value of this configuration parameter as an additional input to the rake command (e.g., rake apipie:static_swagger_json[2.0,form_data]).


This parameter is only relevant if swagger_content_type_input is :json.

If true: the schema of the "in": "body" parameter of each method is given its own entry in the definitions section, and is referenced using $ref from the method definition.

If false: the body parameter definitions are inlined within the method definitions.

If true: in addition to tagging methods with the name of the resource they belong to, methods for which warnings have been issued will be tagged with.

If false: no warnings will be suppressed

If true: all warnings will be suppressed

If an array of values (e.g., [100,102,107]), only the warnings identified by the numbers in the array will be suppressed.


The value to place in the swagger host field.

Default is localhost:3000

If nil then then host field will not be included.


If false (default): response descriptions in the generated swagger will include an additional-properties: false field

If true: the additional-properties: false field will not be included in response object descriptions

Known limitations of the current implementation

  • There is currently no way to document the structure and content-type of the data returned from a method
  • Recorded examples are currently not included in the generated swagger file
  • The apipie formats value is ignored.
  • It is not possible to specify the "consumed" content type on a per-method basis
  • It is not possible to leverage all of the parameter type/format capabilities of swagger
  • Only OpenAPI 2.0 is supported
  • Responses are defined inline and not as a $ref

Dynamic Swagger generation

To generate swagger dynamically, use http://localhost:3000/apipie.json?type=swagger.

Note that authorization is not supported for dynamic swagger generation, so if config.authorize is defined, dynamic swagger generation will be disabled.

Dynamically generated swagger is not cached, and is always generated on the fly.

JSON checksums

If the API client needs to be sure that the JSON didn't changed, add the ApipieChecksumInHeaders middleware in your rails app. It can add a checksum of the entire JSON document in the response headers.


Apipie bindings uses this feature to refresh its JSON cache.

To set it up add the following to your application.rb

require 'apipie/middleware/checksum_in_headers'
# Add JSON checksum in headers for smarter caching
config.middleware.use "Apipie::Middleware::ChecksumInHeaders"

And in your apipie initializer allow checksum calculation

Apipie.configuration.update_checksum = true

By default the header is added to responses for config.doc_base_url and /api. It can be changed in configuration (see Configuration Reference for details).

The checksum calculation is lazy, and done with the first request. If you run with use_cache = true, do not forget to run the rake task apipie:cache.

Tests Integration

Apipie integrates with automated testing in two ways. Documentation bootstrapping and examples recording.

Documentation Bootstrapping

Let's say you have an application without REST API documentation. However you have a set of tests that are run against this API. A lot of information is already included in these tests, it just needs to be extracted somehow. Luckily, Apipie provides such a feature.

When running the tests, set the APIPIE_RECORD=params environment variable or call Apipie.record('params') from specs starter. You can either use it with functional tests:

APIPIE_RECORD=params rake test:functionals

or you can run your server with this param, in case you run the tests against running server:

APIPIE_RECORD=params rails server

When the process quits, the data from requests/responses are used to determine the documentation. It's quite raw, but it makes the initial phase much easier.

Examples Recording

You can also use the tests to generate up-to-date examples for your code. Similar to the bootstrapping process, you can use it with functional tests or a running server, setting APIPIE_RECORD=examples or calling Apipie.record('examples') in your specs starter.

APIPIE_RECORD=examples rake test:functionals
APIPIE_RECORD=examples rails server

The data is written into doc/apipie_examples.yml. By default, only the first example is shown for each action. You can customize this by setting the show_in_doc attribute at each example.

You can add a title to the examples (useful when showing more than one example per method) by adding a 'title' attribute.

--- !omap
  - announcements#index:
    - !omap
      - title: This is a custom title for this example
      - verb: :GET
      - path: /api/blabla/1
      - versions:
        - '1.0'
      - query:
      - request_data:
      - response_data:
      - code: 200
      - show_in_doc: 1   # If 1, show. If 0, do not show.
      - recorded: true

In RSpec you can add metadata to examples. We can use that feature to mark selected examples - the ones that perform the requests that we want to show as examples in the documentation.

For example, we can add show_in_doc to examples, like this:

describe "This is the correct path" do
  it "some test", :show_in_doc do

context "These are edge cases" do
  it "Can't authenticate" do

   it "record not found" do

And then configure RSpec in this way:

RSpec.configure do |config|
  config.treat_symbols_as_metadata_keys_with_true_values = true
  config.filter_run :show_in_doc => true if ENV['APIPIE_RECORD']

This way, when running in recording mode, only the tests that have been marked with the :show_in_doc metadata will be run, and hence only those will be used as examples.


Make sure to enable config.render_views in your config/rails_helper.rb or config/spec_helper.rb if you're using jbuilder, or you will get back empty results

Bindings Generator

In earlier versions (<= 0.0.13), there was a simple client generator as a part of Apipie gem. As more features and users came to Apipie, there was a greater need for changes on a per project basis. It's hard (or even impossible) to provide a generic solution for the client code. We also don't want to tell you what's the right way to do it (what gems to use, how the API should look like etc.).

Therefore you can't generate client code directly by a rake task in further versions.

There is, however, an even better and more flexible way to reuse your API documentation for this purpose: using the API the Apipie provides in the generator code. Check out our sister project apipie-bindings, as they use exactly this approach. You also don't need to run the service, provided it uses Apipie as a backend.

And if you write one on your own, don't hesitate to share it with us!

Disqus Integration

You can setup Disqus discussion within your documentation. Just set the credentials in the Apipie configuration:

config.disqus_shortname = "MyProjectDoc"

External References