knitr::opts_chunk$set( error = TRUE, collapse = TRUE, comment = "#>", eval = FALSE ) library(attempt)
The stop_if()
, warn_if()
and message_if()
are easy to use functions that send an error, a warning or a message if a condition is met. Each function has its counterpart with _not
that returns a message if the condition is not met.
stop_if_not()
is quite the same as assert_that()
from the {assertthat}
package, except that it can takes mappers. It is not the same as base stopifnot()
, as it doesn't take a list of expression.
These functions are also flexible as you can pass base predicates (is.numeric, is.character...), a custom predicate built with mappers, or even your own predicate function.
You can either choose a custom message or just let the built-in messages be printed:
x <- 12 # Stop if .x is numeric stop_if(.x = x, .p = is.numeric) y <- "20" # stop if .x is not numeric stop_if_not(.x = y, .p = is.numeric, msg = "y should be numeric") a <- "this is not numeric" # Warn if .x is charcter warn_if(.x = a, .p = is.character) b <- 20 # Warn if .x is not equal to 10 warn_if_not(.x = b, .p = ~ .x == 10 , msg = "b should be 10") c <- "a" # Message if c is a character message_if(.x = c, .p = is.character, msg = "You entered a character element") # Build more complex predicates d <- 100 message_if(.x = d, .p = ~ sqrt(.x) < 42, msg = "The square root of your element must be more than 42") # Or, if you're kind of old school, you can still pass classic functions e <- 30 message_if(.x = e, .p = function(vec){ return(sqrt(vec) < 42) }, msg = "The square root of your element must be more than 42")
If you need to call a function that takes no argument at .p
(like curl::has_internet()
), use this function as .x
.
stop_if(.x = curl::has_internet(), msg = "You shouldn't have internet to do that") warn_if(.x = curl::has_internet(), msg = "You shouldn't have internet to do that") message_if(.x = curl::has_internet(), msg = "Huray, you have internet \\o/")
If you don't specify a .p
, the default test is isTRUE()
.
a <- is.na(airquality$Ozone) message_if_any(a, msg = "NA found")
That can come really handy inside a function:
my_fun <- function(x){ stop_if_not(.x = curl::has_internet(), msg = "You should have internet to do that") warn_if_not(x, is.character, msg = "x is not a character vector. The output may not be what you're expecting.") paste(x, "is the value.") } my_fun(head(iris))
stop_if()
, warn_if()
and message_if()
all have complementary tests with _all
, _any
and _none
, which combine the if_*
and the warn_*
, stop_*
and message_*
seen before. They take a list as first argument, and a predicate. They test if any, all or none of the elements validate the predicate.
stop_if_any(iris, is.factor, msg = "Factors here. This might be due to stringsAsFactors.") warn_if_none(1:10, ~ .x < 0, msg = "You need to have at least one number under zero.") message_if_all(1:100, is.numeric, msg = "That makes a lot of numbers.")
on_error()
on_error()
behaves as on.exit()
except it happens only when there is an error in the function.
y <- function(x){ on_error(~ print("ouch")) log(x) } y(12) [1] 2.484907 y("a") Error in log(x) : non-numeric argument to mathematical function [1] "ouch"
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