Assert that every element of a list is of a given type

Checks that x is a list and that each of its elements is of type. Type names are matched as in is.character(), is.numeric(), is.integer(), is.double(), is.logical(), is.complex(), is.factor(), and is.list(); any other name is matched against each element's class with inherits() (for example "Date").

Usage

assert_list_of(
  x,
  type,
  null_ok = FALSE,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

x: Object to check.
type: Single string naming the type every element must be.
null_ok: Single logical. If TRUE, a NULL value passes the check without error. Use this for optional arguments that default to NULL. Defaults to FALSE, so NULL is rejected unless you opt in.
arg: Name used to refer to x in error messages. Defaults to the name of the expression passed as x.
call: Environment used as the error's call context. Defaults to the calling function, so errors point at the user's code.

The input x, invisibly.

assert_list_of(list("a", "b", "c"), "character")
assert_list_of(list(1, 2, 3), "numeric")