Is an Argument a List of Objects of a Specific S3 Class or Type?

Checks if an argument is a list of objects inheriting from the S3 class or type specified.

assert_list_of(
  arg,
  cls,
  named = FALSE,
  optional = TRUE,
  arg_name = rlang::caller_arg(arg),
  message = NULL,
  class = "assert_list_of",
  call = parent.frame()
)

Arguments

arg

A function argument to be checked

Default value

none

cls

The S3 class or type to check for

Default value

none

named

If set to TRUE, an error is issued if not all elements of the list are named.

Default value

FALSE

optional

Is the checked argument optional? If set to FALSE and arg is NULL then an error is thrown

Default value

TRUE

arg_name

string indicating the label/symbol of the object being checked.

Default value

rlang::caller_arg(arg)

message

string passed to cli::cli_abort(message). When NULL, default messaging is used (see examples for default messages). "{arg_name}" can be used in messaging.

Default value

NULL

class

Subclass of the condition.

call

The execution environment of a currently running function, e.g. call = caller_env(). The corresponding function call is retrieved and mentioned in error messages as the source of the error.

You only need to supply call when throwing a condition from a helper function which wouldn't be relevant to mention in the message.

Can also be NULL or a defused function call to respectively not display any call or hard-code a code to display.

For more information about error calls, see Including function calls in error messages.

Value

The function throws an error if arg is not a list or if arg is a list but its elements are not objects inheriting from class or of type class. Otherwise, the input is returned invisibly.

See also

Checks for valid input and returns warning or errors messages: assert_atomic_vector(), assert_character_scalar(), assert_character_vector(), assert_data_frame(), assert_date_vector(), assert_expr(), assert_expr_list(), assert_filter_cond(), assert_function(), assert_integer_scalar(), assert_list_element(), assert_logical_scalar(), assert_named(), assert_numeric_vector(), assert_one_to_one(), assert_param_does_not_exist(), assert_s3_class(), assert_same_type(), assert_symbol(), assert_unit(), assert_vars(), assert_varval_list()

Examples

example_fun <- function(list) {
  assert_list_of(list, "data.frame")
}

example_fun(list(mtcars, iris))

try(example_fun(list(letters, 1:10)))
#> Error in example_fun(list(letters, 1:10)) : 
#>   Each element of the list in argument `list` must be class/type
#> <data.frame>.
#> ℹ But, element 1 is a character vector, and element 2 is an integer vector

try(example_fun(c(TRUE, FALSE)))
#> Error in example_fun(c(TRUE, FALSE)) : 
#>   Argument `list` must be class <list>, but is a logical vector.

example_fun2 <- function(list) {
  assert_list_of(list, "numeric", named = TRUE)
}
try(example_fun2(list(1, 2, 3, d = 4)))
#> Error in example_fun2(list(1, 2, 3, d = 4)) : 
#>   All elements of `list` argument must be named.
#> ℹ The indices of the unnamed elements are 1, 2, and 3