Assert that certain conditions are true.

Description

assert_that is a drop-in replacement for stopifnot but is designed to give informative error messages.

Usage

assert_that(..., env = parent.frame())

see_if(..., env = parent.frame())

Arguments

Assertions

Assertion functions should return a single TRUE or FALSE: any other result is an error, and assert_that will complain about it. This will always be the case for the assertions provided by assertthat, but you may need be a more careful for base R functions.

To make your own assertions that work with assert_that, see the help for on_failure.

See Also

validate_that, which returns a message (not an error) if the condition is false.

Examples

x <- 1
# assert_that() generates errors, so can't be usefully run in
# examples
## Not run: 
assert_that(is.character(x))
assert_that(length(x) == 3)
assert_that(is.dir("asdf"))
y <- tempfile()
writeLines("", y)
assert_that(is.dir(y))

## End(Not run)

# But see_if just returns the values, so you'll see that a lot
# in the examples: but remember to use assert_that in your code.
see_if(is.character(x))
see_if(length(x) == 3)
see_if(is.dir(17))
see_if(is.dir("asdf"))

Results