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Is an Argument an Object of a Specific S3 Class?

Source: R/assertions.R
assert_s3_class.Rd

Checks if an argument is an object inheriting from the S3 class specified.

Usage

assert_s3_class(
  arg,
  cls,
  optional = FALSE,
  arg_name = rlang::caller_arg(arg),
  message = NULL,
  class = "assert_s3_class",
  call = parent.frame()
)

Arguments

arg

A function argument to be checked

cls

The S3 class to check for

optional

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

arg_name

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

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.

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 an object which does not inherit from 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_list_of(), assert_logical_scalar(), assert_named(), assert_numeric_vector(), assert_one_to_one(), assert_param_does_not_exist(), assert_same_type(), assert_symbol(), assert_unit(), assert_vars(), assert_varval_list()

Examples

example_fun <- function(obj) {
  assert_s3_class(obj, "factor")
}

example_fun(as.factor(letters))

try(example_fun(letters))
#> Error in example_fun(letters) : 
#>   Argument `obj` must be class <factor>, but is a character vector.

try(example_fun(1:10))
#> Error in example_fun(1:10) : 
#>   Argument `obj` must be class <factor>, but is an integer vector.