http_condition function

Generate a classed http condition.

This function generate S3 condition objects which are passed to stop() or warning() to generate classes warnings and error. These can be used in conjunction with tryCatch()

to respond differently to different type of failure.

http_condition(x, type, task = NULL, call = sys.call(-1))

Arguments

• x: a response, or numeric http code (or other object with status_code method)
• type: type of condition to generate. Must be one of error, warning or message.
• task: The text of the message: either NULL or a character vector. If non-NULL, the error message will finish with "Failed to task".
• call: The call stored in the condition object.

Returns

An S3 object that inherits from (e.g.) condition, type, http_error, http_400 and http_404.

Examples

## Not run:

# You can use tryCatch to take different actions based on the type
# of error. Note that tryCatch will call the first handler that
# matches any classes of the condition, not the best matching, so
# always list handlers from most specific to least specific
f <- function(url) {
  tryCatch(stop_for_status(GET(url)),
    http_404 = function(c) "That url doesn't exist",
    http_403 = function(c) "You need to authenticate!",
    http_400 = function(c) "You made a mistake!",
    http_500 = function(c) "The server screwed up"
  )
}
f("http://httpbin.org/status/404")
f("http://httpbin.org/status/403")
f("http://httpbin.org/status/505")
## End(Not run)

See Also

http://adv-r.had.co.nz/Exceptions-Debugging.html#condition-handling

for more details about R's condition handling model