Check if an object is of a specific object-oriented programming type

Check that an object is an S3, S4, S7, or R6 object.

Usage

check_s3(x, ..., allow_null = FALSE, arg = caller_arg(x), call = caller_env())

check_s4(x, ..., allow_null = FALSE, arg = caller_arg(x), call = caller_env())

check_s7(x, ..., allow_null = FALSE, arg = caller_arg(x), call = caller_env())

check_r6(x, ..., allow_null = FALSE, arg = caller_arg(x), call = caller_env())

Arguments

x

An object to check.

...

Additional arguments passed to cli_abort() which forwards unmatched arguments to abort().

allow_null

Whether x is allowed to be NULL.

arg

An argument name as a string. This argument will be mentioned in error messages as the input that is at the origin of a problem.

call

The execution environment of a currently running function, e.g. caller_env(). The function will be mentioned in error messages as the source of the error. See the call argument of abort() for more information.

Value

NULL invisibly if the check passes, otherwise an error is thrown.

Details

S3 checks are performed by checking if the object has a class attribute with is.object() and is not an S4 object.

S4 checks are performed using isS4().

S7 and R6 checks are performed by checking for the inheritance of the S7_object and R6 classes, respectively.

See also

Other checks: array-type-checks, forbidden-value-checks, inheritance-checks, path-checks, property-checks, s3-type-checks, scalar-type-checks, scalar-value-checks, type-checks, walk-check

Examples

check_s3(factor("a"))
check_s3(1:3) |> try()
#> Error in eval(expr, envir) : 
#>   `1:3` must be an <S3> object, not <integer>.

methods::setClass("Person",
  slots = c(name = "character", age = "numeric")
)
x <- methods::new("Person", name = "John", age = 30)

check_s4(x)
check_s4(factor("a")) |> try()
#> Error in eval(expr, envir) : 
#>   `factor("a")` must be an <S4> object, not <factor>.

# trivial examples of inheritance checks for S7 and R6 objects
x <- structure(list(), class = "S7_object")
check_s7(x)
check_s7(factor("a")) |> try()
#> Error in eval(expr, envir) : 
#>   `factor("a")` must inherit from <S7_object>, but is class <factor>.

x <- structure(list(), class = "R6")
check_r6(x)
check_r6(factor("a")) |> try()
#> Error in eval(expr, envir) : 
#>   `factor("a")` must inherit from <R6>, but is class <factor>.