A client to help you paginate

Value

a list, with objects of class HttpResponse(). Responses are returned in the order they are passed in.

Details

See HttpClient() for information on parameters

R6 classes

This is an R6 class from the package R6. Find out more about R6 at https://r6.r-lib.org/. After creating an instance of an R6 class (e.g., x <- HttpClient$new(url = "https://httpbin.org")) you can access values and methods on the object x.

Methods to paginate

Supported now:

  • limit_offset: the most common way (in my experience), so is the default. This method involves setting how many records and what record to start at for each request. We send these query parameters for you.

  • page_perpage: set the page to fetch and (optionally) how many records to get per page

Supported later, hopefully:

  • link_headers: link headers are URLS for the next/previous/last request given in the response header from the server. This is relatively uncommon, though is recommended by JSONAPI and is implemented by a well known API (GitHub).

  • cursor: this works by a single string given back in each response, to be passed in the subsequent response, and so on until no more records remain. This is common in Solr

Public fields

http_req

an object of class HttpClient

by

(character) how to paginate. Only 'limit_offset' supported for now. In the future will support 'link_headers' and 'cursor'. See Details.

chunk

(numeric/integer) the number by which to chunk requests, e.g., 10 would be be each request gets 10 records. number is passed through format() to prevent larger numbers from being scientifically formatted

limit_param

(character) the name of the limit parameter. Default: limit

offset_param

(character) the name of the offset parameter. Default: offset

limit

(numeric/integer) the maximum records wanted. number is passed through format() to prevent larger numbers from being scientifically formatted

page_param

(character) the name of the page parameter. Default: NULL

per_page_param

(character) the name of the per page parameter. Default: NULL

progress

(logical) print a progress bar, using utils::txtProgressBar. Default: FALSE.

Methods


Method print()

print method for Paginator objects

Usage

Paginator$print(x, ...)

Arguments

x

self

...

ignored


Method new()

Create a new Paginator object

Usage

Paginator$new(
  client,
  by = "limit_offset",
  limit_param = NULL,
  offset_param = NULL,
  limit = NULL,
  chunk = NULL,
  page_param = NULL,
  per_page_param = NULL,
  progress = FALSE
)

Arguments

client

an object of class HttpClient, from a call to HttpClient

by

(character) how to paginate. Only 'limit_offset' supported for now. In the future will support 'link_headers' and 'cursor'. See Details.

limit_param

(character) the name of the limit parameter. Default: limit

offset_param

(character) the name of the offset parameter. Default: offset

limit

(numeric/integer) the maximum records wanted

chunk

(numeric/integer) the number by which to chunk requests, e.g., 10 would be be each request gets 10 records

page_param

(character) the name of the page parameter.

per_page_param

(character) the name of the per page parameter.

progress

(logical) print a progress bar, using utils::txtProgressBar. Default: FALSE.

Returns

A new Paginator object


Method get()

make a paginated GET request

Usage

Paginator$get(path = NULL, query = list(), ...)

Arguments

path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest


Method post()

make a paginated POST request

Usage

Paginator$post(
  path = NULL,
  query = list(),
  body = NULL,
  encode = "multipart",
  ...
)

Arguments

path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest


Method put()

make a paginated PUT request

Usage

Paginator$put(
  path = NULL,
  query = list(),
  body = NULL,
  encode = "multipart",
  ...
)

Arguments

path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest


Method patch()

make a paginated PATCH request

Usage

Paginator$patch(
  path = NULL,
  query = list(),
  body = NULL,
  encode = "multipart",
  ...
)

Arguments

path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest


Method delete()

make a paginated DELETE request

Usage

Paginator$delete(
  path = NULL,
  query = list(),
  body = NULL,
  encode = "multipart",
  ...
)

Arguments

path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest


Method head()

make a paginated HEAD request

Usage

Paginator$head(path = NULL, ...)

Arguments

path

URL path, appended to the base URL

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Details

not sure if this makes any sense or not yet


Method responses()

list responses

Usage

Paginator$responses()

Returns

a list of HttpResponse objects, empty list before requests made


Method status_code()

Get HTTP status codes for each response

Usage

Paginator$status_code()

Returns

numeric vector, empty numeric vector before requests made


Method status()

List HTTP status objects

Usage

Paginator$status()

Returns

a list of http_code objects, empty list before requests made


Method parse()

parse content

Usage

Paginator$parse(encoding = "UTF-8")

Arguments

encoding

(character) the encoding to use in parsing. default:"UTF-8"

Returns

character vector, empty character vector before requests made


Method content()

Get raw content for each response

Usage

Paginator$content()

Returns

raw list, empty list before requests made


Method times()

curl request times

Usage

Paginator$times()

Returns

list of named numeric vectors, empty list before requests made


Method url_fetch()

get the URL that would be sent (i.e., before executing the request) the only things that change the URL are path and query parameters; body and any curl options don't change the URL

Usage

Paginator$url_fetch(path = NULL, query = list())

Arguments

path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

Returns

URLs (character)

Examples

\dontrun{
cli <- HttpClient$new(url = "https://api.crossref.org")
cc <- Paginator$new(client = cli, limit_param = "rows",
   offset_param = "offset", limit = 50, chunk = 10)
cc$url_fetch('works')
cc$url_fetch('works', query = list(query = "NSF"))
}


Method clone()

The objects of this class are cloneable with this method.

Usage

Paginator$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

if (FALSE) {
if (interactive()) {
# limit/offset approach
con <- HttpClient$new(url = "https://api.crossref.org")
cc <- Paginator$new(client = con, limit_param = "rows",
   offset_param = "offset", limit = 50, chunk = 10)
cc
cc$get('works')
cc
cc$responses()
cc$status()
cc$status_code()
cc$times()
# cc$content()
cc$parse()
lapply(cc$parse(), jsonlite::fromJSON)

# page/per page approach (with no per_page param allowed)
conn <- HttpClient$new(url = "https://discuss.ropensci.org")
cc <- Paginator$new(client = conn, by = "page_perpage",
 page_param = "page", per_page_param = "per_page", limit = 90, chunk = 30)
cc
cc$get('c/usecases/l/latest.json')
cc$responses()
lapply(cc$parse(), jsonlite::fromJSON)

# page/per_page
conn <- HttpClient$new('https://api.inaturalist.org')
cc <- Paginator$new(conn, by = "page_perpage", page_param = "page",
 per_page_param = "per_page", limit = 90, chunk = 30)
cc
cc$get('v1/observations', query = list(taxon_name="Helianthus"))
cc$responses()
res <- lapply(cc$parse(), jsonlite::fromJSON)
res[[1]]$total_results
vapply(res, "[[", 1L, "page")
vapply(res, "[[", 1L, "per_page")
vapply(res, function(w) NROW(w$results), 1L)
## another
ccc <- Paginator$new(conn, by = "page_perpage", page_param = "page",
 per_page_param = "per_page", limit = 500, chunk = 30, progress = TRUE)
ccc
ccc$get('v1/observations', query = list(taxon_name="Helianthus"))
res2 <- lapply(ccc$parse(), jsonlite::fromJSON)
vapply(res2, function(w) NROW(w$results), 1L)

# progress bar
(con <- HttpClient$new(url = "https://api.crossref.org"))
cc <- Paginator$new(client = con, limit_param = "rows",
   offset_param = "offset", limit = 50, chunk = 10,
   progress = TRUE)
cc
cc$get('works')
}}

## ------------------------------------------------
## Method `Paginator$url_fetch`
## ------------------------------------------------

if (FALSE) {
cli <- HttpClient$new(url = "https://api.crossref.org")
cc <- Paginator$new(client = cli, limit_param = "rows",
   offset_param = "offset", limit = 50, chunk = 10)
cc$url_fetch('works')
cc$url_fetch('works', query = list(query = "NSF"))
}