Check if a character is a member of a set of valid items

check_member() and check_is_member() functions check whether a given character is a valid member of a specified set of valid items. check_member() raises an error if the character is not part of the valid items, and allows setting a default value if specified. check_is_member() returns TRUE if the character is a valid member, and FALSE otherwise.

Usage

check_member(char, valid_items, default = NULL, par_name = "vec")

check_is_member(char, valid_items, default = NULL)

Arguments

char: A character scalar to check.
valid_items: A vector containing valid items.
default: An optional default value to return if char is not a valid item. If NULL, an error is raised.
par_name: An optional name of the parameter to display in error messages.

Value

check_member(): Returns the original value of char if it is valid, otherwise raises an error or returns the default value.
check_is_member(): Logical value, TRUE if char is a valid member of valid_items, and FALSE otherwise.

Examples

# Examples for check_member()
# ---------------------------
v <- c("apple", "banana", "cherry")
check_member("apple", valid_items = v)
#> [1] "apple"

try(check_member("grape", valid_items = v))
#> Error in check_member("grape", valid_items = v) : 
#>   Expected 'vec' to be one of: 'apple', 'banana', 'cherry' but got 'grape'

check_member("grape", valid_items = v, default = "banana")
#> [1] "banana"

try(check_member(123, valid_items = v))
#> Error in check_member(123, valid_items = v) : 
#>   Expected 'vec' to be one of: 'apple', 'banana', 'cherry' but got 123

check_member("apple", valid_items = v, default = "banana") 
#> [1] "apple"

# Examples for check_is_member()
# ------------------------------

check_is_member("apple", valid_items = v)
#> [1] TRUE

check_is_member("grape", valid_items = v)
#> [1] FALSE

check_is_member("grape", valid_items = v, default = "banana")
#> [1] TRUE

check_is_member(123, valid_items = v)
#> [1] FALSE

check_is_member("apple", valid_items = v, default = "banana") 
#> [1] TRUE