Package validator
Package validator implements value validations for structs and individual fields based on tags.
It has the following unique features:
- Cross Field and Cross Struct validations by using validation tags or custom validators.
- Slice, Array and Map diving, which allows any or all levels of a multidimensional field to be validated.
- Handles type interface by determining it's underlying type prior to validation.
- Handles custom field types such as sql driver Valuer see Valuer
- Alias validation tags, which allows for mapping of several validations to a single tag for easier defining of validations on structs
- Extraction of custom defined Field Name e.g. can specify to extract the JSON name while validating and have it available in the resulting FieldError
Installation
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"
Error Return Value
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)Usage and documentation
Please see http://godoc.org/gopkg.in/go-playground/validator.v8 for detailed usage docs.
Examples:
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
}Benchmarks
Run on MacBook Pro (Retina, 15-inch, Late 2013) 2.6 GHz Intel Core i7 16 GB 1600 MHz DDR3 using Go version go1.5.3 darwin/amd64
go test -cpu=4 -bench=. -benchmem=true
PASS
BenchmarkFieldSuccess-4 10000000 167 ns/op 0 B/op 0 allocs/op
BenchmarkFieldFailure-4 2000000 701 ns/op 432 B/op 4 allocs/op
BenchmarkFieldDiveSuccess-4 500000 2937 ns/op 480 B/op 27 allocs/op
BenchmarkFieldDiveFailure-4 500000 3536 ns/op 912 B/op 31 allocs/op
BenchmarkFieldCustomTypeSuccess-4 5000000 341 ns/op 32 B/op 2 allocs/op
BenchmarkFieldCustomTypeFailure-4 2000000 679 ns/op 432 B/op 4 allocs/op
BenchmarkFieldOrTagSuccess-4 1000000 1157 ns/op 16 B/op 1 allocs/op
BenchmarkFieldOrTagFailure-4 1000000 1109 ns/op 464 B/op 6 allocs/op
BenchmarkStructLevelValidationSuccess-4 2000000 694 ns/op 176 B/op 6 allocs/op
BenchmarkStructLevelValidationFailure-4 1000000 1311 ns/op 640 B/op 11 allocs/op
BenchmarkStructSimpleCustomTypeSuccess-4 2000000 894 ns/op 80 B/op 5 allocs/op
BenchmarkStructSimpleCustomTypeFailure-4 1000000 1496 ns/op 688 B/op 11 allocs/op
BenchmarkStructPartialSuccess-4 1000000 1229 ns/op 384 B/op 10 allocs/op
BenchmarkStructPartialFailure-4 1000000 1838 ns/op 832 B/op 15 allocs/op
BenchmarkStructExceptSuccess-4 2000000 961 ns/op 336 B/op 7 allocs/op
BenchmarkStructExceptFailure-4 1000000 1218 ns/op 384 B/op 10 allocs/op
BenchmarkStructSimpleCrossFieldSuccess-4 2000000 954 ns/op 128 B/op 6 allocs/op
BenchmarkStructSimpleCrossFieldFailure-4 1000000 1569 ns/op 592 B/op 11 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldSuccess-4 1000000 1588 ns/op 192 B/op 10 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldFailure-4 1000000 2217 ns/op 656 B/op 15 allocs/op
BenchmarkStructSimpleSuccess-4 2000000 925 ns/op 48 B/op 3 allocs/op
BenchmarkStructSimpleFailure-4 1000000 1650 ns/op 688 B/op 11 allocs/op
BenchmarkStructSimpleSuccessParallel-4 5000000 261 ns/op 48 B/op 3 allocs/op
BenchmarkStructSimpleFailureParallel-4 2000000 758 ns/op 688 B/op 11 allocs/op
BenchmarkStructComplexSuccess-4 300000 5868 ns/op 544 B/op 32 allocs/op
BenchmarkStructComplexFailure-4 200000 10767 ns/op 3912 B/op 77 allocs/op
BenchmarkStructComplexSuccessParallel-4 1000000 1559 ns/op 544 B/op 32 allocs/op
BenchmarkStructComplexFailureParallel-4 500000 3747 ns/op 3912 B/op 77 allocsComplimentary Software
Here is a list of software that compliments using this library either pre or post validation.
- Gorilla Schema - Package gorilla/schema fills a struct with form values.
- Conform - Trims, sanitizes & scrubs data based on struct tags.
How to Contribute
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.
License
Distributed under MIT License, please see license file in code for more details.