I have the following piece of code:
func GetUUIDValidator(text string) bool { r, _ := regexp.Compile("/[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12}/") return r.Match([]byte(text)) } But when I pass fbd3036f-0f1c-4e98-b71c-d4cd61213f90 as a value, I got false, while indeed it is an UUID v4.
What am I doing wrong?
Regex is expensive. The following approach is ~18x times faster than the regex version.
Use something like https://godoc.org/github.com/google/uuid#Validate instead.
import "github.com/google/uuid" if err := uuid.Validate("uuid..."); err == nil { // valid UUID } [Jan 2025] Updated to use Validate instead of Parse, which was added in v1.5.0.
Try with...
func IsValidUUID(uuid string) bool { r := regexp.MustCompile("^[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}$") return r.MatchString(uuid) } Live example: https://play.golang.org/p/a4Z-Jn4EvG
Note: as others have said, validating UUIDs with regular expressions can be slow. Consider other options too if you need better performance.
[a-f] and sometimes [aAbB], thereby allowing uppercase letters only in a few places.You can utilize satori/go.uuid package to accomplish this:
import "github.com/satori/go.uuid" func IsValidUUID(u string) bool { _, err := uuid.FromString(u) return err == nil } This package is widely used for UUID operations: https://github.com/satori/go.uuid
In case you would be validating it as attribute of a struct, there is an awesome golang library straight from the Go called validator https://godoc.org/gopkg.in/go-playground/validator.v9 which you can use to validate all kinds of fields nested structures by provided built-in validators as well as complete custom validation methods. All you need to do is just add proper tags to the fields
import "gopkg.in/go-playground/validator.v9" type myObject struct { UID string `validate:"required,uuid4"` } func validate(obj *myObject) { validate := validator.New() err := validate.Struct(obj) } It provides structured field errors and other relevant data from it.
validator.v10 is out (v9 is on maintenance only since 2019, meaning it won't receive any further features, just bug & security fixes), although the docs still refer to v9!Since Dec 12, 2023 there is a new feature to validate directly by string: https://github.com/google/uuid/commit/9ee7366e66c9ad96bab89139418a713dc584ae29
var string anyUUID = "elmo" err := uuid.Validate(anyUUID) // will result in an error Live example: https://go.dev/play/p/QIzW63S0Oda
This is very useful when it comes to testing:
assert.NoError(t, uuid.Validate(anyUUID)) 
regex.MustCompilefor usage like the one in your code. Also, Go style regexes don't use // delimiters. Read the documentation to understand how Go regex work.