Check arguments and generate readable error messages.
When creating functions for other people to use, you always need to
erify serves the exact purpose.
Install erify from CRAN:
install.packages("erify")
Or install the development version from Github:
# install devtools if not
# install.packages("devtools")
devtools::install_github("flujoo/erify")
Suppose you are creating a function which prints a string several times to emphasize it:
# print `what` `n` times
emphasize <- function(what, n) {
for (i in 1:n) {
cat(what, "\n")
}
}
# example
emphasize("You're beautiful!", 3)
#> You're beautiful!
#> You're beautiful!
#> You're beautiful!
And suppose a novice user accidentally passes a function to argument
what
, he/she will get an error message which is not very readable:
emphasize(c, 3)
#> Error in cat(what, "\n"): argument 1 (type 'builtin') cannot be handled by 'cat'
You can improve this by adding erify’s check_type()
into
emphasize()
:
emphasize <- function(what, n) {
# check the type of `what`
erify::check_type(what, "character")
# main
for (i in 1:n) {
cat(what, "\n")
}
}
emphasize(c, 3)
#> Error: `what` must have type character.
#>
#> ✖ `what` has type builtin.
In the above code, check_type(what, "character")
checks if what
has
type character, and if not, generates improved error message.
You can add more functions to check arguments, customize error messages, and create your own check functions.
See vignette("erify")
for a gentle introduction to erify.
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