v_enum() returns a validator function that checks if a value is a single
character value matching one of a predefined set of choices. This is useful
for options that must be one of several allowed values.
v_enum(choices)A validator function that takes a value x and raises an error if:
x is not a single character value
x is not in the predefined choices
# Create a validator for one of several color choices
validator <- v_enum(choices = c("red", "green", "blue"))
# Valid inputs
validator("red")
validator("blue")
# Invalid inputs (would raise errors)
try(validator("yellow")) # not in choices
#> Error : must be one of: red, green, blue
try(validator(c("red", "blue"))) # vector, not scalar
#> Error : must be a single character value
try(validator(1)) # numeric, not character
#> Error : must be a single character value