class ActiveResource::Base

ActiveResource::Base is the main class for mapping RESTful resources as models in a Rails application.

For an outline of what Active Resource is capable of, see its README.

Automated mapping ↑

Active Resource objects represent your RESTful resources as manipulatable Ruby objects. To map resources to Ruby objects, Active Resource only needs a class name that corresponds to the resource name (e.g., the class Person maps to the resources people, very similarly to Active Record) and a site value, which holds the URI of the resources.

class Person < ActiveResource::Base
  self.site = "https://api.people.com"
end

Now the Person class is mapped to RESTful resources located at https://api.people.com/people/, and you can now use Active Resource’s life cycle methods to manipulate resources. In the case where you already have an existing model with the same name as the desired RESTful resource you can set the element_name value.

class PersonResource < ActiveResource::Base
  self.site = "https://api.people.com"
  self.element_name = "person"
end

If your Active Resource object is required to use an HTTP proxy you can set the proxy value which holds a URI.

class PersonResource < ActiveResource::Base
  self.site = "https://api.people.com"
  self.proxy = "https://user:password@proxy.people.com:8080"
end

Life cycle methods ↑

Active Resource exposes methods for creating, finding, updating, and deleting resources from REST web services.

ryan = Person.new(:first => 'Ryan', :last => 'Daigle')
ryan.save                # => true
ryan.id                  # => 2
Person.exists?(ryan.id)  # => true
ryan.exists?             # => true

ryan = Person.find(1)
# Resource holding our newly created Person object

ryan.first = 'Rizzle'
ryan.save                # => true

ryan.destroy             # => true

As you can see, these are very similar to Active Record’s life cycle methods for database records. You can read more about each of these methods in their respective documentation.

Custom REST methods ↑

Since simple CRUD/life cycle methods can’t accomplish every task, Active Resource also supports defining your own custom REST methods. To invoke them, Active Resource provides the get, post, put and delete methods where you can specify a custom REST method name to invoke.

# POST to the custom 'register' REST method, i.e. POST /people/new/register.json.
Person.new(:name => 'Ryan').post(:register)
# => { :id => 1, :name => 'Ryan', :position => 'Clerk' }

# PUT an update by invoking the 'promote' REST method, i.e. PUT /people/1/promote.json?position=Manager.
Person.find(1).put(:promote, :position => 'Manager')
# => { :id => 1, :name => 'Ryan', :position => 'Manager' }

# GET all the positions available, i.e. GET /people/positions.json.
Person.get(:positions)
# => [{:name => 'Manager'}, {:name => 'Clerk'}]

# DELETE to 'fire' a person, i.e. DELETE /people/1/fire.json.
Person.find(1).delete(:fire)

For more information on using custom REST methods, see the ActiveResource::CustomMethods documentation.

Validations ↑

You can validate resources client side by overriding validation methods in the base class.

class Person < ActiveResource::Base
   self.site = "https://api.people.com"
   protected
     def validate
       errors.add("last", "has invalid characters") unless last =~ /[a-zA-Z]*/
     end
end

See the ActiveResource::Validations documentation for more information.

Authentication ↑

Many REST APIs require authentication. The HTTP spec describes two ways to make requests with a username and password (see RFC 2617).

Basic authentication simply sends a username and password along with HTTP requests. These sensitive credentials are sent unencrypted, visible to any onlooker, so this scheme should only be used with SSL.

Digest authentication sends a cryptographic hash of the username, password, HTTP method, URI, and a single-use secret key provided by the server. Sensitive credentials aren’t visible to onlookers, so digest authentication doesn’t require SSL. However, this doesn’t mean the connection is secure! Just the username and password.

Another common way to authenticate requests is via bearer tokens, a scheme originally created as part of the OAuth 2.0 protocol (see RFC 6750).

Bearer authentication sends a token, that can maybe only be a short string of hexadecimal characters or even a JWT Token. Similarly to the Basic authentication, this scheme should only be used with SSL.

(You really, really want to use SSL. There’s little reason not to.)

Picking an authentication scheme ↑

Basic authentication is the default. To switch to digest or bearer token authentication, set auth_type to :digest or :bearer:

class Person < ActiveResource::Base
  self.auth_type = :digest
end

Setting the username and password ↑

Set user and password on the class, or include them in the site URL.

class Person < ActiveResource::Base
  # Set user and password directly:
  self.user = "ryan"
  self.password = "password"

  # Or include them in the site:
  self.site = "https://ryan:password@api.people.com"
end

Setting the bearer token ↑

Set bearer_token on the class:

class Person < ActiveResource::Base
  # Set bearer token directly:
  self.auth_type = :bearer
  self.bearer_token = "my-bearer-token"
end

Certificate Authentication ↑

You can also authenticate using an X509 certificate. See ssl_options= for all options.

class Person < ActiveResource::Base
  self.site = "https://secure.api.people.com/"

  File.open(pem_file_path, 'rb') do |pem_file|
    self.ssl_options = {
      cert:        OpenSSL::X509::Certificate.new(pem_file),
      key:         OpenSSL::PKey::RSA.new(pem_file),
      ca_path:     "/path/to/OpenSSL/formatted/CA_Certs",
      verify_mode: OpenSSL::SSL::VERIFY_PEER }
  end
end

Errors & Validation ↑

Error handling and validation is handled in much the same manner as you’re used to seeing in Active Record. Both the response code in the HTTP response and the body of the response are used to indicate that an error occurred.

Resource errors ↑

When a GET is requested for a resource that does not exist, the HTTP 404 (Resource Not Found) response code will be returned from the server which will raise an ActiveResource::ResourceNotFound exception.

# GET https://api.people.com/people/999.json
ryan = Person.find(999) # 404, raises ActiveResource::ResourceNotFound

404 is just one of the HTTP error response codes that Active Resource will handle with its own exception. The following HTTP response codes will also result in these exceptions:

These custom exceptions allow you to deal with resource errors more naturally and with more precision rather than returning a general HTTP error. For example:

begin
  ryan = Person.find(my_id)
rescue ActiveResource::ResourceNotFound
  redirect_to :action => 'not_found'
rescue ActiveResource::ResourceConflict, ActiveResource::ResourceInvalid
  redirect_to :action => 'new'
end

When a GET is requested for a nested resource and you don’t provide the prefix_param an ActiveResource::MissingPrefixParam will be raised.

class Comment < ActiveResource::Base
  self.site = "https://someip.com/posts/:post_id"
end

Comment.find(1)
# => ActiveResource::MissingPrefixParam: post_id prefix_option is missing

Validation errors ↑

Active Resource supports validations on resources and will return errors if any of these validations fail (e.g., “First name can not be blank” and so on). These types of errors are denoted in the response by a response code of 422 and an JSON or XML representation of the validation errors. The save operation will then fail (with a false return value) and the validation errors can be accessed on the resource in question.

ryan = Person.find(1)
ryan.first # => ''
ryan.save  # => false

# When
# PUT https://api.people.com/people/1.xml
# or
# PUT https://api.people.com/people/1.json
# is requested with invalid values, the response is:
#
# Response (422):
# <errors><error>First cannot be empty</error></errors>
# or
# {"errors":{"first":["cannot be empty"]}}
#

ryan.errors.invalid?(:first)  # => true
ryan.errors.full_messages     # => ['First cannot be empty']

For backwards-compatibility with older endpoints, the following formats are also supported in JSON responses:

# {"errors":['First cannot be empty']}
#   This was the required format for previous versions of ActiveResource
# {"first":["cannot be empty"]}
#   This was the default format produced by respond_with in ActionController <3.2.1

Parsing either of these formats will result in a deprecation warning.

Learn more about Active Resource’s validation features in the ActiveResource::Validations documentation.

Timeouts ↑

Active Resource relies on HTTP to access RESTful APIs and as such is inherently susceptible to slow or unresponsive servers. In such cases, your Active Resource method calls could timeout. You can control the amount of time before Active Resource times out with the timeout variable.

class Person < ActiveResource::Base
  self.site = "https://api.people.com"
  self.timeout = 5
end

This sets the timeout to 5 seconds. You can adjust the timeout to a value suitable for the RESTful API you are accessing. It is recommended to set this to a reasonably low value to allow your Active Resource clients (especially if you are using Active Resource in a Rails application) to fail-fast (see en.wikipedia.org/wiki/Fail-fast) rather than cause cascading failures that could incapacitate your server.

When a timeout occurs, an ActiveResource::TimeoutError is raised. You should rescue from ActiveResource::TimeoutError in your Active Resource method calls.

Internally, Active Resource relies on Ruby’s Net::HTTP library to make HTTP requests. Setting timeout sets the read_timeout of the internal Net::HTTP instance to the same value. The default read_timeout is 60 seconds on most Ruby implementations.

Active Resource also supports distinct open_timeout (time to connect) and read_timeout (how long to wait for an upstream response). This is inline with supported Net::HTTP timeout configuration and allows for finer control of client timeouts depending on context.

class Person < ActiveResource::Base
  self.site = "https://api.people.com"
  self.open_timeout = 2
  self.read_timeout = 10
end