canvas-api

Canvas API

This ruby library is to make it easier to use the Canvas API.

Installation

This is packaged as the canvas-api rubygem, so you can just add the dependency to your Gemfile or install the gem on your system:

gem install canvas-api

To require the library in your project:

require 'canvas-api'

Usage

OAuth Dance

Before you can make API calls you need an access token on behalf of the current user. In order to get an access token you'll need to do the OAuth dance (and for that you'll need a client_id and secret. Talk to the Canvas admin about getting these values):

canvas = Canvas::API.new(:host => "https://canvas.example.com", :client_id => 123, :secret => "abcdef")
url = canvas.oauth_url("https://my.site/oauth_success")
# => "https://canvas.example.com/login/oauth2/auth?client_id=123&response_type=code&redirect_uri=http%3A%2F%2Fmy.site%2Foauth_success
redirect to(url)

And then when the browser redirects to oauth_success:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :client_id => 123, :secret => "abcdef")
code = params['code']
canvas.retrieve_access_token(code, 'https://my.site/oauth_success') # this callback_url must match the one provided in the first step
# => {access_token: "qwert"}

General API Calls

Once you've got an access token for a user you should save it (securely!) for future use. To use the API call:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
canvas.get("/api/v1/users/self/profile")
# => {id: 90210, name: "Annie Wilson", ... }

For POST and PUT requests the second parameter is the form parameters to append, either as a hash or an array of arrays:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
canvas.put("/api/v1/users/self", {'user[name]' => 'Dixon Wilson', 'user[short_name]' => 'Dixon'})
# => {id: 90210, name: "Dixon Wilson", ... }
canvas.put("/api/v1/users/self", {'user' => {'name' => 'Dixon Wilson', 'short_name' => 'Dixon'}}) # this is synonymous with the previous call
# => {id: 90210, name: "Dixon Wilson", ... }
canvas.put("/api/v1/users/self", [['user[name]', 'Dixon Wilson'],['user[short_name]', 'Dixon']]) # this is synonymous with the previous call
# => {id: 90210, name: "Dixon Wilson", ... }

On GET requests you can either append query parameters to the actual path or as a hashed second argument:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
canvas.get("/api/v1/users/self/enrollments?type[]=TeacherEnrollment&type[]=TaEnrollment")
# => [{id: 1234, course_id: 5678, ... }, {id: 2345, course_id: 6789, ...}]
canvas.get("/api/v1/users/self/enrollments", {'type' => ['TeacherEnrollment', 'TaEnrollment']}) # this is synonymous with the previous call
# => [{id: 1234, course_id: 5678, ... }, {id: 2345, course_id: 6789, ...}]

Pagination

API endpoints that return lists are often paginated, meaning they will only return the first X results (where X depends on the endpoint and, possibly, the per_page parameter you optionally set). To get more results you'll need to make additional API calls:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
list = canvas.get("/api/v1/calendar_events?all_events=true")
list.length
# => 50
list.more?
# => true (if there's another page of results)
list.next_page!
# => [...] (returns the next page of results)
list.length
# => 100 (also concatenates the results on to the previous list, if that's more convenient)
list.next_page!
# => [...]
list.length
# => 150

Additional Utilities

There are also some helper methods that can make some of the other tricky parts of the Canvas API a little more approachable.

File Uploads

Uploading files ia typically a multi-step process. There are three different ways to upload files.

Upload a file from the local file system:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
canvas.upload_file_from_local("/api/v1/users/self/files", File.open("/path/to/file.jpg"), :content_type => "image/jpeg")
# => {id: 1, display_name: "file.jpg", ... }

Upload a file synchronously from a remote URL:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
canvas.upload_file_from_url("/api/v1/users/self/files", :name => "image.jpg", :size => 12345, :url => "http://www.example.com/image.jpg")
# => {id: 1, display_name: "image.jpg", ... }

Upload a file asynchronouysly from a remote URL:

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
status_url = canvas.upload_file_from_url("/api/v1/users/self/files", :asynch => true, :name => "image.jpg", :size => 12345, :url => "http://www.example.com/image.jpg")
# => "/api/v1/file_status/url"
canvas.get(status_url)
# => {upload_status: "pending"}
canvas.get(status_url)
# => {upload_status: "ready", attachment: {id: 1, display_name: "image.jpg", ... } }

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
status_url = canvas.upload_file_from_url("/api/v1/users/self/files", :asynch => true, :name => "image.jpg", :size => 12345, :url => "http://www.example.com/image.jpg")
# => "/api/v1/file_status/url"
canvas.get(status_url)
# => {upload_status: "errored", message: "Invalid response code, expected 200 got 404"}

For any of these upload types you can optionally provide additional configuration parameters if the upload endpoint is to an area of Canvas that supports folders (user files, course files, etc.)

canvas = Canvas::API.new(:host => "https://canvas.example.com", :token => "qwert")
#
# upload the file to a known folder with id 1234
canvas.upload_file_from_url("/api/v1/users/self/files", :parent_folder_id => 1234, :name => "image.jpg", :size => 12345, :url => "http://www.example.com/image.jpg")
# => {id: 1, display_name: "image.jpg", ... }
#
# upload the file to a folder with the path "/friends"
canvas.upload_file_from_url("/api/v1/users/self/files", :parent_folder_path => "/friends", :name => "image.jpg", :size => 12345, :url => "http://www.example.com/image.jpg")
# => {id: 1, display_name: "image.jpg", ... }
#
# rename this file instead of overwriting a file with the same name (overwrite is the default)
canvas.upload_file_from_url("/api/v1/users/self/files", :on_duplicate => "rename", :name => "image.jpg", :size => 12345, :url => "http://www.example.com/image.jpg")
# => {id: 1, display_name: "image.jpg", ... }

SIS ID Encoding

In addition to regular IDs, Canvas supports SIS IDs defined by other systems. Sometimes these IDs contain non-standard characters, which can cause problems when trying to use them via the API. In those cases you can do the following:

sis_course_id = canvas.encode_id("sis_course_id", "r#-789")
# => "hex:sis_course_id:72232d373839"
canvas.get("/api/v1/courses/#{sis_course_id}/enrollments")
# => [...]