constants | attributes | methods
Class

ActiveResource::Base

Inheritance
< Object

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 files/vendor/rails/activeresource/README.html.

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 = "http://api.people.com:3000/"
  end

Now the Person class is mapped to RESTful resources located at api.people.com:3000/people/, and you can now use Active Resource‘s lifecycles 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 = "http://api.people.com:3000/"
    self.element_name = "person"
  end

Lifecycle 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 lifecycle methods for database records. You can read more about each of these methods in their respective documentation.

Custom REST methods

Since simple CRUD/lifecycle 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.xml.
  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.xml?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.xml.
  Person.get(:positions)
  # => [{:name => 'Manager'}, {:name => 'Clerk'}]

  # DELETE to 'fire' a person, i.e. DELETE /people/1/fire.xml.
  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 = "http://api.people.com:3000/"
     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 will require authentication, usually in the form of basic HTTP authentication. Authentication can be specified by:

  • putting the credentials in the URL for the site variable. 
     class Person < ActiveResource::Base
   self.site = "http://ryan:password@api.people.com:3000/"
 end
  • defining user and/or password variables 
     class Person < ActiveResource::Base
   self.site = "http://api.people.com:3000/"
   self.user = "ryan"
   self.password = "password"
 end

For obvious security reasons, it is probably best if such services are available over HTTPS.

Note: Some values cannot be provided in the URL passed to site. e.g. email addresses as usernames. In those situations you should use the separate user and password option.

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 http://api.people.com:3000/people/999.xml
  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

Validation errors

Active Resource supports validations on resources and will return errors if any 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 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 http://api.people.com:3000/people/1.xml
  # is requested with invalid values, the response is:
  #
  # Response (422):
  # <errors type="array"><error>First cannot be empty</error></errors>
  #

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

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 = "http://api.people.com:3000/"
    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.

Aliases

Method Alias Description
collection_name= → set_collection_name
element_name= → set_element_name
prefix= → set_prefix
primary_key= → set_primary_key
respond_to? → respond_to_without_attributes? For checking respond_to? without searching the attributes (which is faster).

Methods

Class

Visibility Signature
public collection_path (prefix_options = {}, query_options = nil)
public connection (refresh = false)
public create (attributes = {})
public delete (id, options = {})
public element_path (id, prefix_options = {}, query_options = nil)
public exists? (id, options = {})
public find (*arguments)
public format ()
public format= (mime_type_reference_or_format)
public headers ()
public new (attributes = {})
public password ()
public password= (password)
public prefix (options={})
public prefix= (value = '/')
public prefix_source ()
public site ()
public site= (site)
public timeout ()
public timeout= (timeout)
public user ()
public user= (user)

Instance

Visibility Signature
public == (other)
public clone ()
public destroy ()
public dup ()
public encode (options={})
public eql? (other)
public exists? ()
public hash ()
public id ()
public id= (id)
public load (attributes)
public new? ()
public new_record? ()
public reload ()
public respond_to? (method, include_priv = false)
public save ()
public to_json (options={})
public to_param ()
public to_xml (options={})
protected collection_path (options = nil)
protected connection (refresh = false)
protected create ()
protected element_path (options = nil)
protected id_from_response (response)
protected load_attributes_from_response (response)
protected update ()

Class Method Detail

collection_path(prefix_options = {}, query_options = nil)

Gets the collection path for the REST resources. If the query_options parameter is omitted, Rails will split from the prefix_options.

Options

  • prefix_options - A hash to add a prefix to the request for nested URL‘s (e.g., :account_id => 19 would yield a URL like /accounts/19/purchases.xml).
  • query_options - A hash to add items to the query string for the request.

Examples

  Post.collection_path
  # => /posts.xml

  Comment.collection_path(:post_id => 5)
  # => /posts/5/comments.xml

  Comment.collection_path(:post_id => 5, :active => 1)
  # => /posts/5/comments.xml?active=1

  Comment.collection_path({:post_id => 5}, {:active => 1})
  # => /posts/5/comments.xml?active=1

connection(refresh = false)

An instance of ActiveResource::Connection that is the base \connection to the remote service. The refresh parameter toggles whether or not the \connection is refreshed at every request or not (defaults to false).

create(attributes = {})

Creates a new resource instance and makes a request to the remote service that it be saved, making it equivalent to the following simultaneous calls: 

  ryan = Person.new(:first => 'ryan')
  ryan.save

Returns the newly created resource. If a failure has occurred an exception will be raised (see save). If the resource is invalid and has not been saved then valid? will return false, while new? will still return true.

Examples

  Person.create(:name => 'Jeremy', :email => 'myname@nospam.com', :enabled => true)
  my_person = Person.find(:first)
  my_person.email # => myname@nospam.com

  dhh = Person.create(:name => 'David', :email => 'dhh@nospam.com', :enabled => true)
  dhh.valid? # => true
  dhh.new?   # => false

  # We'll assume that there's a validation that requires the name attribute
  that_guy = Person.create(:name => '', :email => 'thatguy@nospam.com', :enabled => true)
  that_guy.valid? # => false
  that_guy.new?   # => true

delete(id, options = {})

Deletes the resources with the ID in the id parameter.

Options

All options specify \prefix and query parameters.

Examples

  Event.delete(2) # sends DELETE /events/2

  Event.create(:name => 'Free Concert', :location => 'Community Center')
  my_event = Event.find(:first) # let's assume this is event with ID 7
  Event.delete(my_event.id) # sends DELETE /events/7

  # Let's assume a request to events/5/cancel.xml
  Event.delete(params[:id]) # sends DELETE /events/5

element_path(id, prefix_options = {}, query_options = nil)

Gets the element path for the given ID in id. If the query_options parameter is omitted, Rails will split from the \prefix options.

Options

prefix_options - A \hash to add a \prefix to the request for nested URLs (e.g., :account_id => 19 

                   would yield a URL like <tt>/accounts/19/purchases.xml</tt>).

query_options - A \hash to add items to the query string for the request.

Examples

  Post.element_path(1)
  # => /posts/1.xml

  Comment.element_path(1, :post_id => 5)
  # => /posts/5/comments/1.xml

  Comment.element_path(1, :post_id => 5, :active => 1)
  # => /posts/5/comments/1.xml?active=1

  Comment.element_path(1, {:post_id => 5}, {:active => 1})
  # => /posts/5/comments/1.xml?active=1

exists?(id, options = {})

Asserts the existence of a resource, returning true if the resource is found.

Examples

  Note.create(:title => 'Hello, world.', :body => 'Nothing more for now...')
  Note.exists?(1) # => true

  Note.exists(1349) # => false

find(*arguments)

Core method for finding resources. Used similarly to Active Record‘s find method.

Arguments

The first argument is considered to be the scope of the query. That is, how many resources are returned from the request. It can be one of the following.

  • :one - Returns a single resource.
  • :first - Returns the first resource found.
  • :last - Returns the last resource found.
  • :all - Returns every resource that matches the request.

Options

  • :from - Sets the path or custom method that resources will be fetched from.
  • :params - Sets query and \prefix (nested URL) parameters.

Examples

  Person.find(1)
  # => GET /people/1.xml

  Person.find(:all)
  # => GET /people.xml

  Person.find(:all, :params => { :title => "CEO" })
  # => GET /people.xml?title=CEO

  Person.find(:first, :from => :managers)
  # => GET /people/managers.xml

  Person.find(:last, :from => :managers)
  # => GET /people/managers.xml

  Person.find(:all, :from => "/companies/1/people.xml")
  # => GET /companies/1/people.xml

  Person.find(:one, :from => :leader)
  # => GET /people/leader.xml

  Person.find(:all, :from => :developers, :params => { :language => 'ruby' })
  # => GET /people/developers.xml?language=ruby

  Person.find(:one, :from => "/companies/1/manager.xml")
  # => GET /companies/1/manager.xml

  StreetAddress.find(1, :params => { :person_id => 1 })
  # => GET /people/1/street_addresses/1.xml

format()

Returns the current format, default is ActiveResource::Formats::XmlFormat.

format=(mime_type_reference_or_format)

Sets the format that attributes are sent and received in from a mime type reference: 

  Person.format = :json
  Person.find(1) # => GET /people/1.json

  Person.format = ActiveResource::Formats::XmlFormat
  Person.find(1) # => GET /people/1.xml

Default format is :xml.

headers()

new(attributes = {})

Constructor method for \new resources; the optional attributes parameter takes a \hash of attributes for the \new resource.

Examples

  my_course = Course.new
  my_course.name = "Western Civilization"
  my_course.lecturer = "Don Trotter"
  my_course.save

  my_other_course = Course.new(:name => "Philosophy: Reason and Being", :lecturer => "Ralph Cling")
  my_other_course.save

password()

Gets the \password for REST HTTP authentication.

password=(password)

Sets the \password for REST HTTP authentication.

prefix(options={})

Gets the \prefix for a resource‘s nested URL (e.g., prefix/collectionname/1.xml) This method is regenerated at runtime based on what the \prefix is set to.

prefix=(value = '/')

Sets the \prefix for a resource‘s nested URL (e.g., prefix/collectionname/1.xml). Default value is site.path.

prefix_source()

An attribute reader for the source string for the resource path \prefix. This method is regenerated at runtime based on what the \prefix is set to.

site()

Gets the URI of the REST resources to map for this class. The site variable is required for Active Resource‘s mapping to work.

site=(site)

Sets the URI of the REST resources to map for this class to the value in the site argument. The site variable is required for Active Resource‘s mapping to work.

timeout()

Gets the number of seconds after which requests to the REST API should time out.

timeout=(timeout)

Sets the number of seconds after which requests to the REST API should time out.

user()

Gets the \user for REST HTTP authentication.

user=(user)

Sets the \user for REST HTTP authentication.

Instance Method Detail

==(other)

Test for equality. Resource are equal if and only if other is the same object or is an instance of the same class, is not new?, and has the same id.

Examples

  ryan = Person.create(:name => 'Ryan')
  jamie = Person.create(:name => 'Jamie')

  ryan == jamie
  # => false (Different name attribute and id)

  ryan_again = Person.new(:name => 'Ryan')
  ryan == ryan_again
  # => false (ryan_again is new?)

  ryans_clone = Person.create(:name => 'Ryan')
  ryan == ryans_clone
  # => false (Different id attributes)

  ryans_twin = Person.find(ryan.id)
  ryan == ryans_twin
  # => true

clone()

Returns a \clone of the resource that hasn‘t been assigned an id yet and is treated as a \new resource. 

  ryan = Person.find(1)
  not_ryan = ryan.clone
  not_ryan.new?  # => true

Any active resource member attributes will NOT be cloned, though all other attributes are. This is to prevent the conflict between any prefix_options that refer to the original parent resource and the newly cloned parent resource that does not exist. 

  ryan = Person.find(1)
  ryan.address = StreetAddress.find(1, :person_id => ryan.id)
  ryan.hash = {:not => "an ARes instance"}

  not_ryan = ryan.clone
  not_ryan.new?            # => true
  not_ryan.address         # => NoMethodError
  not_ryan.hash            # => {:not => "an ARes instance"}

destroy()

Deletes the resource from the remote service.

Examples

  my_id = 3
  my_person = Person.find(my_id)
  my_person.destroy
  Person.find(my_id) # 404 (Resource Not Found)

  new_person = Person.create(:name => 'James')
  new_id = new_person.id # => 7
  new_person.destroy
  Person.find(new_id) # 404 (Resource Not Found)

dup()

Duplicate the current resource without saving it.

Examples

  my_invoice = Invoice.create(:customer => 'That Company')
  next_invoice = my_invoice.dup
  next_invoice.new? # => true

  next_invoice.save
  next_invoice == my_invoice # => false (different id attributes)

  my_invoice.customer   # => That Company
  next_invoice.customer # => That Company

encode(options={})

Returns the serialized string representation of the resource in the configured serialization format specified in ActiveResource::Base.format. The options applicable depend on the configured encoding format.

eql?(other)

Tests for equality (delegates to ==).

exists?()

Evaluates to true if this resource is not new? and is found on the remote service. Using this method, you can check for resources that may have been deleted between the object‘s instantiation and actions on it.

Examples

  Person.create(:name => 'Theodore Roosevelt')
  that_guy = Person.find(:first)
  that_guy.exists? # => true

  that_lady = Person.new(:name => 'Paul Bean')
  that_lady.exists? # => false

  guys_id = that_guy.id
  Person.delete(guys_id)
  that_guy.exists? # => false

hash()

Delegates to id in order to allow two resources of the same type and \id to work with something like: 

  [Person.find(1), Person.find(2)] & [Person.find(1), Person.find(4)] # => [Person.find(1)]

id()

Gets the \id attribute of the resource.

id=(id)

Sets the \id attribute of the resource.

load(attributes)

A method to manually load attributes from a \hash. Recursively loads collections of resources. This method is called in initialize and create when a \hash of attributes is provided.

Examples

  my_attrs = {:name => 'J&J Textiles', :industry => 'Cloth and textiles'}
  my_attrs = {:name => 'Marty', :colors => ["red", "green", "blue"]}

  the_supplier = Supplier.find(:first)
  the_supplier.name # => 'J&M Textiles'
  the_supplier.load(my_attrs)
  the_supplier.name('J&J Textiles')

  # These two calls are the same as Supplier.new(my_attrs)
  my_supplier = Supplier.new
  my_supplier.load(my_attrs)

  # These three calls are the same as Supplier.create(my_attrs)
  your_supplier = Supplier.new
  your_supplier.load(my_attrs)
  your_supplier.save

new?()

A method to determine if the resource a \new object (i.e., it has not been POSTed to the remote service yet).

Examples

  not_new = Computer.create(:brand => 'Apple', :make => 'MacBook', :vendor => 'MacMall')
  not_new.new? # => false

  is_new = Computer.new(:brand => 'IBM', :make => 'Thinkpad', :vendor => 'IBM')
  is_new.new? # => true

  is_new.save
  is_new.new? # => false

new_record?()

Alias for new?

reload()

A method to \reload the attributes of this object from the remote web service.

Examples

  my_branch = Branch.find(:first)
  my_branch.name # => "Wislon Raod"

  # Another client fixes the typo...

  my_branch.name # => "Wislon Raod"
  my_branch.reload
  my_branch.name # => "Wilson Road"

respond_to?(method, include_priv = false)

A method to determine if an object responds to a message (e.g., a method call). In Active Resource, a Person object with a name attribute can answer true to my_person.respond_to?(:name), my_person.respond_to?(:name=), and my_person.respond_to?(:name?).

save()

A method to \save (POST) or \update (PUT) a resource. It delegates to create if a \new object, update if it is existing. If the response to the \save includes a body, it will be assumed that this body is XML for the final object as it looked after the \save (which would include attributes like created_at that weren‘t part of the original submit).

Examples

  my_company = Company.new(:name => 'RoleModel Software', :owner => 'Ken Auer', :size => 2)
  my_company.new? # => true
  my_company.save # sends POST /companies/ (create)

  my_company.new? # => false
  my_company.size = 10
  my_company.save # sends PUT /companies/1 (update)

to_json(options={})

Returns a JSON string representing the model. Some configuration is available through options.

Options

The options are passed to the to_json method on each attribute, so the same options as the to_json methods in Active Support.

  • :only - Only include the specified attribute or list of attributes in the serialized output. Attribute names must be specified as strings.
  • :except - Do not include the specified attribute or list of attributes in the serialized output. Attribute names must be specified as strings.

Examples

  person = Person.new(:first_name => "Jim", :last_name => "Smith")
  person.to_json
  # => {"first_name": "Jim", "last_name": "Smith"}

  person.to_json(:only => ["first_name"])
  # => {"first_name": "Jim"}

  person.to_json(:except => ["first_name"])
  # => {"last_name": "Smith"}

to_param()

Allows Active Resource objects to be used as parameters in Action Pack URL generation.

to_xml(options={})

A method to convert the the resource to an XML string.

Options

The options parameter is handed off to the to_xml method on each attribute, so it has the same options as the to_xml methods in Active Support.

  • :indent - Set the indent level for the XML output (default is +2+).
  • :dasherize - Boolean option to determine whether or not element names should replace underscores with dashes (default is false).
  • :skip_instruct - Toggle skipping the +instruct!+ call on the XML builder that generates the XML declaration (default is false).

Examples

  my_group = SubsidiaryGroup.find(:first)
  my_group.to_xml
  # => <?xml version="1.0" encoding="UTF-8"?>
  #    <subsidiary_group> [...] </subsidiary_group>

  my_group.to_xml(:dasherize => true)
  # => <?xml version="1.0" encoding="UTF-8"?>
  #    <subsidiary-group> [...] </subsidiary-group>

  my_group.to_xml(:skip_instruct => true)
  # => <subsidiary_group> [...] </subsidiary_group>

collection_path(options = nil)

connection(refresh = false)

create()

Create (i.e., \save to the remote service) the \new resource.

element_path(options = nil)

id_from_response(response)

Takes a response from a typical create post and pulls the ID out

load_attributes_from_response(response)

update()

Update the resource on the remote service.