Package validator

[](https://gitter.im/go-playground/validator?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)  [](https://semaphoreci.com/joeybloggs/validator) [](https://coveralls.io/github/go-playground/validator?branch=v9) [](https://goreportcard.com/report/github.com/go-playground/validator) [](https://godoc.org/gopkg.in/go-playground/validator.v9) 

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.v9

or to update

go get -u gopkg.in/go-playground/validator.v9

Then import the validator package into your own code.

import "gopkg.in/go-playground/validator.v9"

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:

• http://stackoverflow.com/a/29138676/3158232
• https://github.com/go-playground/validator/issues/134

Validator only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) 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.v9 for detailed usage docs.

Examples:

Struct & Field validation

package main

import (
	"fmt"

	"gopkg.in/go-playground/validator.v9"
)

// 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 of Validate, it caches struct info
var validate *validator.Validate

func main() {

	validate = validator.New()

	validateStruct()
	validateVariable()
}

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 )
	err := validate.Struct(user)
	if err != nil {

		// this check is only needed when your code could produce
		// an invalid value for validation such as interface with nil
		// value most including myself do not usually have code like this.
		if _, ok := err.(*validator.InvalidValidationError); ok {
			fmt.Println(err)
			return
		}

		for _, err := range err.(validator.ValidationErrors) {

			fmt.Println(err.Namespace())
			fmt.Println(err.Field())
			fmt.Println(err.StructNamespace()) // can differ when a custom TagNameFunc is registered or
			fmt.Println(err.StructField())     // by passing alt name to ReportError like below
			fmt.Println(err.Tag())
			fmt.Println(err.ActualTag())
			fmt.Println(err.Kind())
			fmt.Println(err.Type())
			fmt.Println(err.Value())
			fmt.Println(err.Param())
			fmt.Println()
		}

		// from here you can create your own error messages in whatever language you wish
		return
	}

	// save user to database
}

func validateVariable() {

	myEmail := "joeybloggs.gmail.com"

	errs := validate.Var(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.v9"
)

// DbBackedUser User struct
type DbBackedUser struct {
	Name sql.NullString `validate:"required"`
	Age  sql.NullInt64  `validate:"required"`
}

// use a single instance of Validate, it caches struct info
var validate *validator.Validate

func main() {

	validate = validator.New()

	// register all sql.Null* types to use the ValidateValuer CustomTypeFunc
	validate.RegisterCustomTypeFunc(ValidateValuer, sql.NullString{}, sql.NullInt64{}, sql.NullBool{}, sql.NullFloat64{})

	// build object for validation
	x := DbBackedUser{Name: sql.NullString{String: "", Valid: true}, Age: sql.NullInt64{Int64: 0, Valid: false}}

	err := validate.Struct(x)

	if err != nil {
		fmt.Printf("Err(s):\n%+v\n", err)
	}
}

// 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"

	"gopkg.in/go-playground/validator.v9"
)

// 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"`
}

// use a single instance of Validate, it caches struct info
var validate *validator.Validate

func main() {

	validate = validator.New()

	// register validation for 'User'
	// NOTE: only have to register a non-pointer type for 'User', validator
	// interanlly dereferences during it's type checks.
	validate.RegisterStructValidation(UserStructLevelValidation, User{})

	// build 'User' info, normally posted data etc...
	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 InvalidValidationError for bad validation input, nil or ValidationErrors ( []FieldError )
	err := validate.Struct(user)
	if err != nil {

		// this check is only needed when your code could produce
		// an invalid value for validation such as interface with nil
		// value most including myself do not usually have code like this.
		if _, ok := err.(*validator.InvalidValidationError); ok {
			fmt.Println(err)
			return
		}

		for _, err := range err.(validator.ValidationErrors) {

			fmt.Println(err.Namespace())
			fmt.Println(err.Field())
			fmt.Println(err.StructNamespace()) // can differ when a custom TagNameFunc is registered or
			fmt.Println(err.StructField())     // by passing alt name to ReportError like below
			fmt.Println(err.Tag())
			fmt.Println(err.ActualTag())
			fmt.Println(err.Kind())
			fmt.Println(err.Type())
			fmt.Println(err.Value())
			fmt.Println(err.Param())
			fmt.Println()
		}

		// from here you can create your own error messages in whatever language you wish
		return
	}

	// save user to database
}

// 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(sl validator.StructLevel) {

	user := sl.Current().Interface().(User)

	if len(user.FirstName) == 0 && len(user.LastName) == 0 {
		sl.ReportError(user.FirstName, "FirstName", "fname", "fnameorlname", "")
		sl.ReportError(user.LastName, "LastName", "lname", "fnameorlname", "")
	}

	// plus can to more, even with different tag than "fnameorlname"
}

Benchmarks

Run on MacBook Pro (Retina, 15-inch, Late 2013) 2.6 GHz Intel Core i7 16 GB 1600 MHz DDR3 using Go version go1.6.3 darwin/amd64

BenchmarkFieldSuccess-8                                    	10000000	       147 ns/op	       0 B/op	       0 allocs/op
BenchmarkFieldSuccessParallel-8                            	30000000	        42.5 ns/op	       0 B/op	       0 allocs/op
BenchmarkFieldFailure-8                                    	 3000000	       417 ns/op	     192 B/op	       4 allocs/op
BenchmarkFieldFailureParallel-8                            	10000000	       140 ns/op	     192 B/op	       4 allocs/op
BenchmarkFieldDiveSuccess-8                                	 2000000	       876 ns/op	     201 B/op	      11 allocs/op
BenchmarkFieldDiveSuccessParallel-8                        	 5000000	       277 ns/op	     201 B/op	      11 allocs/op
BenchmarkFieldDiveFailure-8                                	 1000000	      1185 ns/op	     396 B/op	      16 allocs/op
BenchmarkFieldDiveFailureParallel-8                        	 3000000	       402 ns/op	     397 B/op	      16 allocs/op
BenchmarkFieldCustomTypeSuccess-8                          	 5000000	       321 ns/op	      32 B/op	       2 allocs/op
BenchmarkFieldCustomTypeSuccessParallel-8                  	20000000	       104 ns/op	      32 B/op	       2 allocs/op
BenchmarkFieldCustomTypeFailure-8                          	 3000000	       416 ns/op	     192 B/op	       4 allocs/op
BenchmarkFieldCustomTypeFailureParallel-8                  	10000000	       150 ns/op	     192 B/op	       4 allocs/op
BenchmarkFieldOrTagSuccess-8                               	 1000000	      1119 ns/op	      16 B/op	       1 allocs/op
BenchmarkFieldOrTagSuccessParallel-8                       	 3000000	       462 ns/op	      16 B/op	       1 allocs/op
BenchmarkFieldOrTagFailure-8                               	 2000000	       715 ns/op	     208 B/op	       5 allocs/op
BenchmarkFieldOrTagFailureParallel-8                       	 3000000	       436 ns/op	     208 B/op	       5 allocs/op
BenchmarkStructLevelValidationSuccess-8                    	 3000000	       399 ns/op	      32 B/op	       2 allocs/op
BenchmarkStructLevelValidationSuccessParallel-8            	20000000	       140 ns/op	      32 B/op	       2 allocs/op
BenchmarkStructLevelValidationFailure-8                    	 2000000	       749 ns/op	     288 B/op	       8 allocs/op
BenchmarkStructLevelValidationFailureParallel-8            	 5000000	       296 ns/op	     288 B/op	       8 allocs/op
BenchmarkStructSimpleCustomTypeSuccess-8                   	 2000000	       673 ns/op	      32 B/op	       2 allocs/op
BenchmarkStructSimpleCustomTypeSuccessParallel-8           	10000000	       213 ns/op	      32 B/op	       2 allocs/op
BenchmarkStructSimpleCustomTypeFailure-8                   	 1000000	      1056 ns/op	     392 B/op	       9 allocs/op
BenchmarkStructSimpleCustomTypeFailureParallel-8           	 3000000	       450 ns/op	     408 B/op	      10 allocs/op
BenchmarkStructPartialSuccess-8                            	 2000000	       789 ns/op	     256 B/op	       6 allocs/op
BenchmarkStructPartialSuccessParallel-8                    	 5000000	       307 ns/op	     256 B/op	       6 allocs/op
BenchmarkStructPartialFailure-8                            	 1000000	      1105 ns/op	     464 B/op	      11 allocs/op
BenchmarkStructPartialFailureParallel-8                    	 5000000	       493 ns/op	     464 B/op	      11 allocs/op
BenchmarkStructExceptSuccess-8                             	 1000000	      1212 ns/op	     480 B/op	      12 allocs/op
BenchmarkStructExceptSuccessParallel-8                     	10000000	       282 ns/op	     240 B/op	       5 allocs/op
BenchmarkStructExceptFailure-8                             	 1000000	      1004 ns/op	     448 B/op	      10 allocs/op
BenchmarkStructExceptFailureParallel-8                     	 5000000	       452 ns/op	     448 B/op	      10 allocs/op
BenchmarkStructSimpleCrossFieldSuccess-8                   	 2000000	       656 ns/op	      72 B/op	       3 allocs/op
BenchmarkStructSimpleCrossFieldSuccessParallel-8           	 5000000	       211 ns/op	      72 B/op	       3 allocs/op
BenchmarkStructSimpleCrossFieldFailure-8                   	 2000000	       968 ns/op	     288 B/op	       8 allocs/op
BenchmarkStructSimpleCrossFieldFailureParallel-8           	 5000000	       406 ns/op	     288 B/op	       8 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldSuccess-8        	 1000000	      1000 ns/op	      80 B/op	       4 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldSuccessParallel-8	 5000000	       334 ns/op	      80 B/op	       4 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldFailure-8        	 1000000	      1324 ns/op	     304 B/op	       9 allocs/op
BenchmarkStructSimpleCrossStructCrossFieldFailureParallel-8	 3000000	       520 ns/op	     304 B/op	       9 allocs/op
BenchmarkStructSimpleSuccess-8                             	 3000000	       534 ns/op	       0 B/op	       0 allocs/op
BenchmarkStructSimpleSuccessParallel-8                     	10000000	       144 ns/op	       0 B/op	       0 allocs/op
BenchmarkStructSimpleFailure-8                             	 1000000	      1039 ns/op	     392 B/op	       9 allocs/op
BenchmarkStructSimpleFailureParallel-8                     	 5000000	       419 ns/op	     392 B/op	       9 allocs/op
BenchmarkStructComplexSuccess-8                            	  500000	      2678 ns/op	     128 B/op	       8 allocs/op
BenchmarkStructComplexSuccessParallel-8                    	 2000000	       874 ns/op	     128 B/op	       8 allocs/op
BenchmarkStructComplexFailure-8                            	  200000	      6342 ns/op	    2833 B/op	      53 allocs/op
BenchmarkStructComplexFailureParallel-8                    	 1000000	      2875 ns/op	    2833 B/op	      53 allocs/op

Complimentary Software

Here is a list of software that compliments using this library either pre or post validation.

• form - Decodes url.Values into Go value(s) and Encodes Go value(s) into url.Values. Dual Array and Full map support.
• Conform - Trims, sanitizes & scrubs data based on struct tags.

How to Contribute

Make a pull request...

License

Distributed under MIT License, please see license file in code for more details.