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Dynamic Open API (Swagger) Client for R
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rapiclient

Build Status CRAN_Status_Badge

Access services specified in OpenAPI (formerly Swagger) format.

rapiclient is not a code generator. Client is generated dynamically as a list of R functions.

Installation

Install the current released version from CRAN:

install.packages("rapiclient")

Or get the current development version from github:

# install.packages("devtools")
devtools::install_github("bergant/rapiclient")

Usage

Prepare API Operations and Schemas

library(rapiclient)

This example uses the sample petstore service and its OpenAPI definition at (http://petstore.swagger.io/v2/swagger.json).

pet_api <- get_api(url = "http://petstore.swagger.io/v2/swagger.json")
operations <- get_operations(pet_api)
schemas <- get_schemas(pet_api)

Function get_operations returns a list of functions. Each function takes named arguments, converts the values to JSON according to API operation definition and performs a service call which returns a http response object.

Function get_schemas returns a list of functions where each function returns an object according to the related schema in the API.

Calling Service Operations

Find a Pet

Let's try to find a pet with Id = 42 (see operation definition):

res <- operations$getPetById(petId = 42)

res$status_code
# [1] 404
str(httr::content(res))
# List of 3
#  $ code   : int 1
#  $ type   : chr "error"
#  $ message: chr "Pet not found"

New Pet

OK, there is no pet with Id = 42, so let's add a pet:

res <- 
  operations$addPet(
    id = 42,
    category = schemas$Category(
      id = 1,
      name = "Undefined"
    ),
    name = "Agrajag",
    photoUrls = list(),
    tags = list(
      schemas$Tag(id = 1, name = "Wild"),
      schemas$Tag(id = 2, name = "Furry")
    ),
    status = "available"
  )

res$status_code
# [1] 200

Check:

res <- operations$getPetById(petId = 42)

res$status_code
# [1] 200
str(httr::content(res))
# List of 6
#  $ id       : int 42
#  $ category :List of 2
#   ..$ id  : int 1
#   ..$ name: chr "Undefined"
#  $ name     : chr "Agrajag"
#  $ photoUrls: list()
#  $ tags     :List of 2
#   ..$ :List of 2
#   .. ..$ id  : int 1
#   .. ..$ name: chr "Wild"
#   ..$ :List of 2
#   .. ..$ id  : int 2
#   .. ..$ name: chr "Furry"
#  $ status   : chr "available"

Response Handlers

If all operations are handled identically (e.g. reading content or stop on http exception), it is more convenient to create the API functions with this functionality. get_operations accepts an optional handler function which must accept a httr response object as an argument.

Some handler functions are already predefined. For example content_or_stop returns a content or throws an exception.

operations <- get_operations(pet_api, handle_response = content_or_stop)

pet_data <- operations$getPetById(42)
str(pet_data)
# List of 6
#  $ id       : int 42
#  $ category :List of 2
#   ..$ id  : int 1
#   ..$ name: chr "Undefined"
#  $ name     : chr "Agrajag"
#  $ photoUrls: list()
#  $ tags     :List of 2
#   ..$ :List of 2
#   .. ..$ id  : int 1
#   .. ..$ name: chr "Wild"
#   ..$ :List of 2
#   .. ..$ id  : int 2
#   .. ..$ name: chr "Furry"
#  $ status   : chr "available"

Note that you can always trace the communication between client and server with httr::with_verbose:

httr::with_verbose({
  # get pet data
  pet_data <- operations$getPetById(42)
  # delete a pet entry
  operations$deletePet(api_key = "special-key", petId = 42)
})
# NULL
# -> GET /v2/pet/42 HTTP/1.1
 -> Host: petstore.swagger.io
 -> User-Agent: libcurl/7.51.0 r-curl/2.3 httr/1.2.1
 -> Accept-Encoding: gzip, deflate
 -> Content-Type: application/json
 -> Accept: application/json
 -> 
 <- HTTP/1.1 200 OK
 <- Date: Tue, 14 Feb 2017 09:15:55 GMT
 <- Access-Control-Allow-Origin: *
 <- Access-Control-Allow-Methods: GET, POST, DELETE, PUT
 <- Access-Control-Allow-Headers: Content-Type, api_key, Authorization
 <- Content-Type: application/json
 <- Connection: close
 <- Server: Jetty(9.2.9.v20150224)
 <- 
 -> DELETE /v2/pet/42 HTTP/1.1
 -> Host: petstore.swagger.io
 -> User-Agent: libcurl/7.51.0 r-curl/2.3 httr/1.2.1
 -> Accept-Encoding: gzip, deflate
 -> Content-Type: application/json
 -> Accept: application/json
 -> Content-Length: 0
 -> 
 <- HTTP/1.1 200 OK
 <- Date: Tue, 14 Feb 2017 09:15:56 GMT
 <- Access-Control-Allow-Origin: *
 <- Access-Control-Allow-Methods: GET, POST, DELETE, PUT
 <- Access-Control-Allow-Headers: Content-Type, api_key, Authorization
 <- Content-Type: application/json
 <- Connection: close
 <- Server: Jetty(9.2.9.v20150224)
 <- 

Help on API Operations

The good news is that autocomplete in RStudio editor works fine with dynamically created functions. The bad news: R documentation is not available with help or ?. To lookup the operation definition just print the function (write it down without parenthesis):

Let's get help for getPetById:

operations$getPetById
# getPetById 
# Find pet by ID 
# Description:
#    Returns a single pet 
# 
# Parameters:
#   petId (integer)
#     ID of pet to return

More complicated addPet also describes the nested schemas:

operations$addPet
# addPet 
# Add a new pet to the store 
# 
# Parameters:
#   id (integer)
#   category (Category)
#   name (string)
#   photoUrls (array[string])
#   tags (array[Tag])
#   status (string)
#     pet status in the store
# Category 
#   id (integer)
#   name (string)
# Tag 
#   id (integer)
#   name (string)

For more detailed operation description use the operation's "definition" attribute :

definition <- attr(operations$getPetById, "definition")
str(definition)
# List of 10
#  $ tags       : chr "pet"
#  $ summary    : chr "Find pet by ID"
#  $ description: chr "Returns a single pet"
#  $ operationId: chr "getPetById"
#  $ produces   : chr [1:2] "application/xml" "application/json"
#  $ parameters :List of 1
#   ..$ :List of 6
#   .. ..$ name       : chr "petId"
#   .. ..$ in         : chr "path"
#   .. ..$ description: chr "ID of pet to return"
#   .. ..$ required   : logi TRUE
#   .. ..$ type       : chr "integer"
#   .. ..$ format     : chr "int64"
#  $ responses  :List of 3
#   ..$ 200:List of 2
#   .. ..$ description: chr "successful operation"
#   .. ..$ schema     :List of 1
#   .. .. ..$ $ref: chr "#/definitions/Pet"
#   ..$ 400:List of 1
#   .. ..$ description: chr "Invalid ID supplied"
#   ..$ 404:List of 1
#   .. ..$ description: chr "Pet not found"
#  $ security   :List of 1
#   ..$ :List of 1
#   .. ..$ api_key: list()
#  $ path       : chr "/pet/{petId}"
#  $ action     : chr "get"

Using Additional Headers

Set additional http headers at the time of creating operation functions in get_operations function.

The following example uses New York Times API from developer.nytimes.com with API key authentication.

nyt_api <- get_api("http://developer.nytimes.com/top_stories_v2.json/swagger.json")

nyt_operations <- 
  get_operations( nyt_api, .headers = c("api-key" = Sys.getenv("NYT_API_KEY")))

res <- nyt_operations$Top_Stories(section = "science", format = "json")

res$status_code
# [1] 200
 
content <- httr::content(res)
str(content, max.level = 1)
# List of 6
#  $ status      : chr "OK"
#  $ copyright   : chr "Copyright (c) 2017 The New York Times Company. All Rights Reserved."
#  $ section     : chr "science"
#  $ last_updated: chr "2017-02-14T04:07:28-05:00"
#  $ num_results : int 26
#  $ results     :List of 26
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