Class | ActiveResource::Base |
In: |
lib/active_resource/base.rb
|
Parent: | 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.
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
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.
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.
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.
Many REST APIs will require authentication, usually in the form of basic HTTP authentication. Authentication can be specified by:
class Person < ActiveResource::Base self.site = "http://ryan:password@api.people.com:3000/" end
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 seperate user and password option.
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.
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
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.
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.
prefix= | -> | set_prefix |
element_name= | -> | set_element_name |
collection_name= | -> | set_collection_name |
primary_key= | -> | set_primary_key |
respond_to? | -> | respond_to_without_attributes? |
For checking respond_to? without searching the attributes (which is faster). |
Gets the collection path for the REST resources. If the query_options parameter is omitted, Rails will split from the prefix_options.
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
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 a new resource instance and request to the remote service that it be saved, making it equivalent to the following simultaneous calls:
ryan = Person.new(:first => 'ryan') ryan.save
The newly created resource is returned. 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.
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
Deletes the resources with the ID in the id parameter.
All options specify prefix and query parameters.
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
Gets the element path for the given ID in id. If the query_options parameter is omitted, Rails will split from the prefix 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.
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
Asserts the existence of a resource, returning true if the resource is found.
Note.create(:title => 'Hello, world.', :body => 'Nothing more for now...') Note.exists?(1) # => true Note.exists(1349) # => false
Core method for finding resources. Used similarly to Active Record‘s find method.
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.
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(: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
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.
Constructor method for new resources; the optional attributes parameter takes a hash of attributes for the new resource.
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
Sets the prefix for a resource‘s nested URL (e.g., prefix/collectionname/1.xml). Default value is site.path.
Gets the URI of the REST resources to map for this class. The site variable is required Active Resource‘s mapping to work.
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.
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
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"}
Deletes the resource from the remote service.
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)
Duplicate the current resource without saving it.
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
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.
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
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.
my_attrs = {:name => 'J&J Textiles', :industry => 'Cloth and textiles'} 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
A method to determine if the resource a new object (i.e., it has not been POSTed to the remote service yet).
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
A method to reload the attributes of this object from the remote web service.
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"
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?").
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).
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)
A method to convert the the resource to an XML string.
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.
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>