Query the Canvas LMS API

This is an extremely minimal client. You need to know the API to be able to use this client. All this function does is:

Try to substitute each listed parameter into endpoint, using the {parameter} or :parameter notation.
If a GET request (the default), then add all other listed parameters as query parameters.
If not a GET request, then send the other parameters in the request body, as JSON.
Convert the response to an R list using jsonlite::fromJSON().

Usage

cnvs(
  endpoint = "/api/v1/courses",
  ...,
  per_page = NULL,
  .per_page = NULL,
  .token = NULL,
  .destfile = NULL,
  .overwrite = FALSE,
  .api_url = NULL,
  .method = "GET",
  .limit = NULL,
  .accept = "application/json",
  .send_headers = NULL,
  .progress = TRUE,
  .params = list(),
  .max_wait = 600,
  .max_rate = NULL
)

Arguments

endpoint

Canvas API endpoint. Defaults to /api/v1/courses which lists your courses. Must be one of the following forms:

METHOD path, e.g. GET /api/v1/courses,
path, e.g. /api/v1/courses,
METHOD url, e.g. GET https://canvas.instructure.com/api/v1/courses,
url, e.g. https://canvas.instructure.com/api/v1/courses.

If the method is not supplied, will use .method, which defaults to "GET".

...

Name-value pairs giving API parameters. Will be matched into endpoint placeholders, sent as query parameters in GET requests, and as a JSON body of POST requests. If there is only one unnamed parameter, and it is a raw vector, then it will not be JSON encoded, but sent as raw data, as is. This can be used for example to add assets to releases. Named NULL values are silently dropped. For GET requests, named NA values trigger an error. For other methods, named NA values are included in the body of the request, as JSON null.

per_page, .per_page

Number of items to return per page. If omitted, will be substituted by max(.limit, 100) if .limit is set, otherwise determined by the API (never greater than 100).

.token

Authentication token. Defaults to cnvs_token().

.destfile

Path to write response to disk. If NULL (default), response will be processed and returned as an object. If path is given, response will be written to disk in the form sent. cnvs writes the response to a temporary file, and renames that file to .destfile after the request was successful. The name of the temporary file is created by adding a -<random>.cnvs-tmp suffix to it, where <random> is an ASCII string with random characters. cnvs removes the temporary file on error.

.overwrite

If .destfile is provided, whether to overwrite an existing file. Defaults to FALSE. If an error happens the original file is kept.

.api_url

Canvas domain URL. Used if endpoint just contains a path. Defaults to CANVAS_DOMAIN environment variable if set.

.method

HTTP method to use if not explicitly supplied in the endpoint.

.limit

Number of records to return. This can be used instead of manual pagination. By default it is NULL, which means that the defaults of the Canvas API are used. You can set it to a number to request more (or less) records, and also to Inf to request all records. Note, that if you request many records, then multiple Canvas API calls are used to get them, and this can take a potentially long time.

.accept

The value of the Accept HTTP header. Defaults to "application/json". If Accept is given in .send_headers, then that will be used.

.send_headers

Named character vector of header field values (except Authorization, which is handled via .token). This can be used to override or augment the default User-Agent header: "https://github.com/cwickham/cnvs".

.progress

Whether to show a progress indicator for calls that need more than one HTTP request.

.params

Additional list of parameters to append to .... It is easier to use this than ... if you have your parameters in a list already.

.max_wait

Maximum number of seconds to wait if rate limited. Defaults to 10 minutes.

.max_rate

Maximum request rate in requests per second. Set this to automatically throttle requests.

Value

Answer from the API as a cnvs_response object, which is also a list. Failed requests will generate an R error. Requests that generate a raw response will return a raw vector.

Examples

if (FALSE) { # \dontrun{
## List your courses
cnvs("/api/v1/courses")

## Get a specific course
cnvs("/api/v1/courses/{course_id}", course_id = 123456)

## Same thing with :param syntax
cnvs("/api/v1/courses/:course_id", course_id = 123456)

## List assignments for a course
cnvs("/api/v1/courses/{course_id}/assignments", course_id = 123456)

## Create an assignment
cnvs(
  "POST /api/v1/courses/{course_id}/assignments",
  course_id = 123456,
  assignment = list(
    name = "Homework 1",
    points_possible = 10
  )
)

## Automatic pagination - get all students
students <- cnvs(
  "/api/v1/courses/{course_id}/users",
  course_id = 123456,
  enrollment_type = "student",
  .limit = Inf
)
} # }

Usage

Arguments

Value

See also

Examples