API Definition

The ApiDefinition class is a singleton where you can define API-wide constructs. Praxis allows you to define the following constructs in your ApiDefinition:

Response Definitions: Reusable response templates (see Response Definitions)
API Information: Global, or versioned, metadata about the api (see API Information).
Traits: A convenient way to share common DSL elements across resource definitions and actions (see traits).

Below is a basic ApiDefinition that defines a response template, general info, and a trait:

Praxis::ApiDefinition.define

  info do
    name 'Some App'
    title 'An example Praxis application'
    description 'A simple application meant for testing purposes'
    base_path '/'
  end

  info '1.0' do
    base_path '/v1'
  end

  response_template :other_response do
    status 200
  end

  trait :authenticated do
    headers do
      key "Auth-Token", String, required: true
    end
  end
end

Praxis::ApiDefinition is a singleton that can be augmented at any point during the bootstrapping process, but before any of your resource definitions are loaded. This allows you to refer to the contents of your ApiDefinition from your resource definitions. See Bootstrapping for more information on the various bootstrapping stages.

Global Information

It is possible to provide global API information in the ApiDefinition.define block with the info method. You may define this metadata for all versions of your API, or only for a specific version. All definitions at the global level (i.e. those that do not specify a version) will be inherited by all versions. Any directive defined within a version will overwrite anything inherited (except base_path and base_params which a version cannot override if they have been set at the default level).

There are several attributes that are only allowed at global level:

endpoint can define your fully qualified API’s endpoint. It’s used purely for documentation purposes and will not be used in any routing or route-generation.
version_with will define what versioning “scheme” your application will use. By default it’s set to [:header, :params], meaning Praxis will look for either an X-Api-Version request header or an api_version query parameter to determine the version of your API to use for processing the request. It is also possible to use a path-based versioning scheme by using version_with :path. See section below for details.
documentation_url is a hint to users where they can find the final version of the API’s documentation.

The rest of the directives are supported in both the global or version level:

name: A short name for your API
title: A title or tagline.
description: A longer description about the API.
base_path: Root path prepended to all routes.
base_params: Default parameters applied to all actions. Used to define any params specified in base_path.
consumes: List of handlers the API accepts from clients (defaults to 'json', 'x-www-form-urlencoded').
produces: List of handlers the API may use to generate responses (defaults to 'json').

Below is a basic ApiDefinition that defines global info, as well info for a specific version:

Praxis::ApiDefinition.define

  info do
    name 'Some App'
    title 'An example Praxis application'
    description 'This is an example application API.'
    endpoint 'api.example.com'
    documentation_url 'https://docs.example.com/some-app/'
    consumes 'json', ''x-www-form-urlencoded''
    produces 'json', 'xml'
    base_path '/:app_name'
    base_params do
      attribute :app_name, String, required: true
    end
  end

  info '1.0' do
    base_path '/v1'
    # override the global description.
    description 'The first stable version of of this example API.'
  end

end

In this example, the given info for version 1.0 would have a description of “The first stable version of of this example API.”, while the base_path would be “/:app_name/v1”.

You can use the base_path and base_param directives to define the base routes and their params for re-use across your whole API, or for a specific version. These are applied “before” any prefixes that you specify in your resources and actions, and will always apply, before, and independently, of any prefix that may be defined.

Path-Based Versioning

If you want to version your API based on request paths, set the version_using directive to :path, and specify an appropriate base_path matcher. This base_path matcher must include an :api_version variable in it (like any other action route) which Praxis will use to extract the exact version string when routing to your resources.

Below is a basic ApiDefinition that uses path-based versioning, and specifies a base_path with the :api_version placeholder:

Praxis::ApiDefinition.define

  info do
    description 'An example an API using path-based versioning'
    version_using :path
    base_path '/api/v:api_version'
  end

  info '1.0' do
    description 'The first stable version of of this example API.'
  end

end

In the above example, Praxis will resolve the base_path for any resources in version “1.0” to “/api/v1.0”.