gopkg.in/go-playground/validator.v8
Package validator implements value validations for structs and individual fields based on tags.
It has the following unique features:
Use go get.
go get gopkg.in/go-playground/validator.v8
or to update
go get -u gopkg.in/go-playground/validator.v8
Then import the validator package into your own code.
import "gopkg.in/go-playground/validator.v8"
Validation functions return type error
They return type error to avoid the issue discussed in the following, where err is always != nil:
validator only returns nil or ValidationErrors as type error; so in you code all you need to do is check if the error returned is not nil, and if it's not type cast it to type ValidationErrors like so:
err := validate.Struct(mystruct)
validationErrors := err.(validator.ValidationErrors)
Please see http://godoc.org/gopkg.in/go-playground/validator.v8 for detailed usage docs.
Struct & Field validation
package main
import (
"fmt"
"gopkg.in/go-playground/validator.v8"
)
// 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() {
config := &validator.Config{TagName: "validate"}
validate = validator.New(config)
validateStruct()
validateField()
}
func validateStruct() {
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 ValidationErrors ( map[string]*FieldError )
errs := validate.Struct(user)
if errs != nil {
fmt.Println(errs) // output: Key: "User.Age" Error:Field validation for "Age" failed on the "lte" tag
// Key: "User.Addresses[0].City" Error:Field validation for "City" failed on the "required" tag
err := errs.(validator.ValidationErrors)["User.Addresses[0].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
}
func validateField() {
myEmail := "joeybloggs.gmail.com"
errs := validate.Field(myEmail, "required,email")
if errs != nil {
fmt.Println(errs) // output: Key: "" Error:Field validation for "" failed on the "email" tag
return
}
// email ok, move on
}
Custom Field Type
package main
import (
"database/sql"
"database/sql/driver"
"fmt"
"reflect"
"gopkg.in/go-playground/validator.v8"
)
// DbBackedUser User struct
type DbBackedUser struct {
Name sql.NullString `validate:"required"`
Age sql.NullInt64 `validate:"required"`
}
func main() {
config := &validator.Config{TagName: "validate"}
validate := validator.New(config)
// register all sql.Null* types to use the ValidateValuer CustomTypeFunc
validate.RegisterCustomTypeFunc(ValidateValuer, sql.NullString{}, sql.NullInt64{}, sql.NullBool{}, sql.NullFloat64{})
x := DbBackedUser{Name: sql.NullString{String: "", Valid: true}, Age: sql.NullInt64{Int64: 0, Valid: false}}
errs := validate.Struct(x)
if len(errs.(validator.ValidationErrors)) > 0 {
fmt.Printf("Errs:\n%+v\n", errs)
}
}
// ValidateValuer implements validator.CustomTypeFunc
func ValidateValuer(field reflect.Value) interface{} {
if valuer, ok := field.Interface().(driver.Valuer); ok {
val, err := valuer.Value()
if err == nil {
return val
}
// handle the error how you want
}
return nil
}
Struct Level Validation
package main
import (
"fmt"
"reflect"
"gopkg.in/go-playground/validator.v8"
)
// User contains user information
type User struct {
FirstName string `json:"fname"`
LastName string `json:"lname"`
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() {
config := &validator.Config{TagName: "validate"}
validate = validator.New(config)
validate.RegisterStructValidation(UserStructLevelValidation, User{})
validateStruct()
}
// UserStructLevelValidation contains custom struct level validations that don't always
// make sense at the field validation level. For Example this function validates that either
// FirstName or LastName exist; could have done that with a custom field validation but then
// would have had to add it to both fields duplicating the logic + overhead, this way it's
// only validated once.
//
// NOTE: you may ask why wouldn't I just do this outside of validator, because doing this way
// hooks right into validator and you can combine with validation tags and still have a
// common error output format.
func UserStructLevelValidation(v *validator.Validate, structLevel *validator.StructLevel) {
user := structLevel.CurrentStruct.Interface().(User)
if len(user.FirstName) == 0 && len(user.LastName) == 0 {
structLevel.ReportError(reflect.ValueOf(user.FirstName), "FirstName", "fname", "fnameorlname")
structLevel.ReportError(reflect.ValueOf(user.LastName), "LastName", "lname", "fnameorlname")
}
// plus can to more, even with different tag than "fnameorlname"
}
func validateStruct() {
address := &Address{
Street: "Eavesdown Docks",
Planet: "Persphone",
Phone: "none",
City: "Unknown",
}
user := &User{
FirstName: "",
LastName: "",
Age: 45,
Email: "Badger.Smith@gmail.com",
FavouriteColor: "#000",
Addresses: []*Address{address},
}
// returns nil or ValidationErrors ( map[string]*FieldError )
errs := validate.Struct(user)
if errs != nil {
fmt.Println(errs) // output: Key: 'User.LastName' Error:Field validation for 'LastName' failed on the 'fnameorlname' tag
// Key: 'User.FirstName' Error:Field validation for 'FirstName' failed on the 'fnameorlname' tag
err := errs.(validator.ValidationErrors)["User.FirstName"]
fmt.Println(err.Field) // output: FirstName
fmt.Println(err.Tag) // output: fnameorlname
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
}
PASS
BenchmarkFieldSuccess-8 20000000 118 ns/op 0 B/op 0 allocs/op
BenchmarkFieldFailure-8 2000000 758 ns/op 432 B/op 4 allocs/op
BenchmarkFieldDiveSuccess-8 500000 2471 ns/op 464 B/op 28 allocs/op
BenchmarkFieldDiveFailure-8 500000 3172 ns/op 896 B/op 32 allocs/op
BenchmarkFieldCustomTypeSuccess-8 5000000 300 ns/op 32 B/op 2 allocs/op
BenchmarkFieldCustomTypeFailure-8 2000000 775 ns/op 432 B/op 4 allocs/op
BenchmarkFieldOrTagSuccess-8 1000000 1122 ns/op 4 B/op 1 allocs/op
BenchmarkFieldOrTagFailure-8 1000000 1167 ns/op 448 B/op 6 allocs/op
BenchmarkStructLevelValidationSuccess-8 3000000 548 ns/op 160 B/op 5 allocs/op
BenchmarkStructLevelValidationFailure-8 3000000 558 ns/op 160 B/op 5 allocs/op
BenchmarkStructSimpleCustomTypeSuccess-8 2000000 623 ns/op 36 B/op 3 allocs/op
BenchmarkStructSimpleCustomTypeFailure-8 1000000 1381 ns/op 640 B/op 9 allocs/op
BenchmarkStructPartialSuccess-8 1000000 1036 ns/op 272 B/op 9 allocs/op
BenchmarkStructPartialFailure-8 1000000 1734 ns/op 730 B/op 14 allocs/op
BenchmarkStructExceptSuccess-8 2000000 888 ns/op 250 B/op 7 allocs/op
BenchmarkStructExceptFailure-8 1000000 1036 ns/op 272 B/op 9 allocs/op
BenchmarkStructSimpleCrossFieldSuccess-8 2000000 773 ns/op 80 B/op 4 allocs/op
BenchmarkStructSimpleCrossFieldFailure-8 1000000 1487 ns/op 536 B/op 9 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldSuccess-8 1000000 1261 ns/op 112 B/op 7 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldFailure-8 1000000 2055 ns/op 576 B/op 12 allocs/op
BenchmarkStructSimpleSuccess-8 3000000 519 ns/op 4 B/op 1 allocs/op
BenchmarkStructSimpleFailure-8 1000000 1429 ns/op 640 B/op 9 allocs/op
BenchmarkStructSimpleSuccessParallel-8 10000000 146 ns/op 4 B/op 1 allocs/op
BenchmarkStructSimpleFailureParallel-8 2000000 551 ns/op 640 B/op 9 allocs/op
BenchmarkStructComplexSuccess-8 500000 3269 ns/op 244 B/op 15 allocs/op
BenchmarkStructComplexFailure-8 200000 8436 ns/op 3609 B/op 60 allocs/op
BenchmarkStructComplexSuccessParallel-8 1000000 1024 ns/op 244 B/op 15 allocs/op
BenchmarkStructComplexFailureParallel-8 500000 3536 ns/op 3609 B/op 60 allocs/op
Here is a list of software that compliments using this library either pre or post validation.
There will always be a development branch for each version i.e. v1-development. In order to contribute,
please make your pull requests against those branches.
If the changes being proposed or requested are breaking changes, please create an issue, for discussion or create a pull request against the highest development branch for example this package has a v1 and v1-development branch however, there will also be a v2-development branch even though v2 doesn't exist yet.
I strongly encourage everyone whom creates a custom validation function to contribute them and help make this package even better.
Distributed under MIT License, please see license file in code for more details.
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