Check if an argument is a function

checkFunction(x, args = NULL, ordered = FALSE, nargs = NULL, null.ok = FALSE)

check_function(x, args = NULL, ordered = FALSE, nargs = NULL, null.ok = FALSE)

assertFunction(
  x,
  args = NULL,
  ordered = FALSE,
  nargs = NULL,
  null.ok = FALSE,
  .var.name = vname(x),
  add = NULL
)

assert_function(
  x,
  args = NULL,
  ordered = FALSE,
  nargs = NULL,
  null.ok = FALSE,
  .var.name = vname(x),
  add = NULL
)

testFunction(x, args = NULL, ordered = FALSE, nargs = NULL, null.ok = FALSE)

test_function(x, args = NULL, ordered = FALSE, nargs = NULL, null.ok = FALSE)

expect_function(
  x,
  args = NULL,
  ordered = FALSE,
  nargs = NULL,
  null.ok = FALSE,
  info = NULL,
  label = vname(x)
)

Arguments

x

[any]
Object to check.

args

[character]
Expected formal arguments. Checks that a function has no arguments if set to character(0). Default is NULL (no check).

ordered

[logical(1)]
Flag whether the arguments provided in args must be the first length(args) arguments of the function in the specified order. Default is FALSE.

nargs

[integer(1)]
Required number of arguments, without .... Default is NULL (no check).

null.ok

[logical(1)]
If set to TRUE, x may also be NULL. In this case only a type check of x is performed, all additional checks are disabled.

.var.name

[character(1)]
Name of the checked object to print in assertions. Defaults to the heuristic implemented in vname.

add

[AssertCollection]
Collection to store assertion messages. See AssertCollection.

info

[character(1)]
Extra information to be included in the message for the testthat reporter. See expect_that.

label

[character(1)]
Name of the checked object to print in messages. Defaults to the heuristic implemented in vname.

Value

Depending on the function prefix: If the check is successful, the functions assertFunction/assert_function return x invisibly, whereas checkFunction/check_function and testFunction/test_function return TRUE. If the check is not successful, assertFunction/assert_function throws an error message, testFunction/test_function returns FALSE, and checkFunction returns a string with the error message. The function expect_function always returns an expectation.

See also

Examples

testFunction(mean)
#> [1] TRUE
testFunction(mean, args = "x")
#> [1] TRUE