package main import ( "fmt" "github.com/go-playground/locales/en" "github.com/go-playground/universal-translator" "gopkg.in/go-playground/validator.v9" en_translations "gopkg.in/go-playground/validator.v9/translations/en" ) // User contains user information type User struct { FirstName string `validate:"required"` LastName string `validate:"required"` Age uint8 `validate:"gte=0,lte=130"` Email string `validate:"required,email"` FavouriteColor string `validate:"iscolor"` // alias for 'hexcolor|rgb|rgba|hsl|hsla' Addresses []*Address `validate:"required,dive,required"` // a person can have a home and cottage... } // Address houses a users address information type Address struct { Street string `validate:"required"` City string `validate:"required"` Planet string `validate:"required"` Phone string `validate:"required"` } // use a single instance , it caches struct info var ( uni *ut.UniversalTranslator validate *validator.Validate ) func main() { // NOTE: ommitting allot of error checking for brevity en := en.New() uni = ut.New(en, en) // this is usually know or extracted from http 'Accept-Language' header // also see uni.FindTranslator(...) trans, _ := uni.GetTranslator("en") validate = validator.New() en_translations.RegisterDefaultTranslations(validate, trans) translateAll(trans) translateIndividual(trans) translateOverride(trans) // yep you can specify your own in whatever locale you want! } func translateAll(trans ut.Translator) { type User struct { Username string `validate:"required"` Tagline string `validate:"required,lt=10"` Tagline2 string `validate:"required,gt=1"` } user := User{ Username: "Joeybloggs", Tagline: "This tagline is way too long.", Tagline2: "1", } err := validate.Struct(user) if err != nil { // translate all error at once errs := err.(validator.ValidationErrors) // returns a map with key = namespace & value = translated error // NOTICE: 2 errors are returned and you'll see something surprising // translations are i18n aware!!!! // eg. '10 characters' vs '1 character' fmt.Println(errs.Translate(trans)) } } func translateIndividual(trans ut.Translator) { type User struct { Username string `validate:"required"` } var user User err := validate.Struct(user) if err != nil { errs := err.(validator.ValidationErrors) for _, e := range errs { // can translate each error one at a time. fmt.Println(e.Translate(trans)) } } } func translateOverride(trans ut.Translator) { validate.RegisterTranslation("required", trans, func(ut ut.Translator) error { return ut.Add("required", "{0} must have a value!", true) // see universal-translator for details }, func(ut ut.Translator, fe validator.FieldError) string { t, _ := ut.T("required", fe.Field()) return t }) type User struct { Username string `validate:"required"` } var user User err := validate.Struct(user) if err != nil { errs := err.(validator.ValidationErrors) for _, e := range errs { // can translate each error one at a time. fmt.Println(e.Translate(trans)) } } }