package main import ( "fmt" "gopkg.in/go-playground/validator.v5" ) // 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:"hexcolor|rgb|rgba"` 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"` } var validate *validator.Validate func main() { validate = validator.New("validate", validator.BakedInValidators) address := &Address{ Street: "Eavesdown Docks", Planet: "Persphone", Phone: "none", } user := &User{ FirstName: "Badger", LastName: "Smith", Age: 135, Email: "Badger.Smith@gmail.com", FavouriteColor: "#000", Addresses: []*Address{address}, } // returns nil or *StructErrors errs := validate.Struct(user) if errs != nil { // err will be of type *FieldError err := errs.Errors["Age"] fmt.Println(err.Error()) // output: Field validation for "Age" failed on the "lte" tag fmt.Println(err.Field) // output: Age fmt.Println(err.Tag) // output: lte fmt.Println(err.Kind) // output: uint8 fmt.Println(err.Type) // output: uint8 fmt.Println(err.Param) // output: 130 fmt.Println(err.Value) // output: 135 // or if you prefer you can use the Flatten function // NOTE: I find this usefull when using a more hard static approach of checking field errors. // The above, is best for passing to some generic code to say parse the errors. i.e. I pass errs // to a routine which loops through the errors, creates and translates the error message into the // users locale and returns a map of map[string]string // field and error which I then use // within the HTML rendering. flat := errs.Flatten() fmt.Println(flat) // output: map[Age:Field validation for "Age" failed on the "lte" tag Addresses[0].Address.City:Field validation for "City" failed on the "required" tag] err = flat["Addresses[0].Address.City"] fmt.Println(err.Field) // output: City fmt.Println(err.Tag) // output: required fmt.Println(err.Kind) // output: string fmt.Println(err.Type) // output: string fmt.Println(err.Param) // output: fmt.Println(err.Value) // output: // from here you can create your own error messages in whatever language you wish return } // save user to database }