Type check allows use of types to
automatically add checking code when types are annotated.
See also typed for a number of
pre-defined common types to be used with typeCheck.
☞ This fork of typeCheck
adds one simple convenience wrapper type_define_lambda on top of
type_define:
# The two type definitions below are identical:
type.my_string_scalar1 <-
type_define_lambda( is.character(.) && length(.)==1 )
type.my_string_scalar2 <-
type_define( function(.)
is.character(.) && length(.)==1 )☞ Use the dot (.) to refer to the parameter of the checking
function.
type_define() is used to define a new type. The check argument
specifies a function used to verify the objects type. type_check adds
the checks to a specific function.
type.numeric <- type_define(check = is.numeric)
#> Error in type_define(check = is.numeric): could not find function "type_define"
f <- type_check(function(x = ? numeric) x)
#> Error in type_check(function(x = `?`(numeric)) x): could not find function "type_check"
f(1)
#> Error in f(1): could not find function "f"
f("txt")
#> Error in f("txt"): could not find function "f"Types are defined as methods of the type generic. This means they
follow the same properties as normal S3 methods and can be exported and
imported to and from packages like all other functions.
The error argument is used to specify a custom error message for a
type.
type.numeric <- type_define(
check = is.numeric,
error = function(obj_name, obj_value, type) {
sprintf("%s: '%s' is not a number!", obj_name, obj_value)
})
#> Error in type_define(check = is.numeric, error = function(obj_name, obj_value, : could not find function "type_define"
f <- type_check(function(x = ? numeric) x)
#> Error in type_check(function(x = `?`(numeric)) x): could not find function "type_check"
f("txt")
#> Error in f("txt"): could not find function "f"When writing a package adding a call to
typeCheck::type_check_package() anywhere outside a function will add
type checks to all functions in the package. Functions without type
annotations are unaltered.
This means it is easy to add annotations in a stepwise process to existing packages.
If you are using roxygen2 You
can use the following importFrom statement (or use the equivalent
importFrom() call directly in the NAMESPACE file.)
f <- function(x = ? numeric) x
#' @importFrom typeCheck type type_define
typeCheck::type_check_package()