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/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.
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 create 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.
Person.new(:name => 'Ryan).post(:register) # => { :id => 1, :name => 'Ryan', :position => 'Clerk' } Person.find(1).put(:promote, :position => 'Manager') # => { :id => 1, :name => 'Ryan', :position => 'Manager' }
For more information on creating and 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 putting the credentials in the site variable of the Active Resource class you need to authenticate.
class Person < ActiveResource::Base self.site = "http://ryan:password@api.people.com:3000/" end
For obvious security reasons, it is probably best if such services are available over HTTPS.
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) # => Raises ActiveResource::ResourceNotFound # => Response = 404
+404+ is just one of the HTTP error response codes that ActiveResource will handle with its own exception. The following HTTP response codes will also result in these exceptions:
200 - 399: | Valid response, no exception |
404: | ActiveResource::ResourceNotFound |
409: | ActiveResource::ResourceConflict |
422: | ActiveResource::ResourceInvalid (rescued by save as validation errors) |
401 - 499: | ActiveResource::ClientError |
500 - 599: | ActiveResource::ServerError |
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.
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.
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. |
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) # => DELETE /events/2 Event.create(:name => 'Free Concert', :location => 'Community Center') my_event = Event.find(:first) # => Events (id: 7) Event.delete(my_event.id) # => DELETE /events/7 # Let's assume a request to events/5/cancel.xml Event.delete(params[:id]) # => 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 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. |
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.
+:one+: | Returns a single resource. |
+:first+: | Returns the first resource found. |
+:all+: | Returns every resource that matches the request. |
from: | Sets the path or custom method that resources will be fetched from. |
params: | Sets query and prefix (nested URL) parameters. |
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(: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. Example:
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 ActiveResource‘s mapping to work.
Sets the URI of the REST resources to map for this class to the value in the site argument. The site variable is required ActiveResource‘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
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 # => POST /companies/ (create) my_company.new? # => false my_company.size = 10 my_company.save # => 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 ActiveSupport.
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). |
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>