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github.com/go-playground/validator

Package validator

v5.0.2+incompatible
Latest Go to latest

The latest major version is v10.

Published: Apr 19, 2015 | License: MIT | Module: github.com/go-playground/validator

Overview

Package validator implements value validations for structs and individual fields based on tags. It can also handle Cross Field and Cross Struct validation for nested structs.

Validate

validate := validator.New("validate", validator.BakedInValidators)

errs := validate.Struct(//your struct)
valErr := validate.Field(field, "omitempty,min=1,max=10")

A simple example usage:

type UserDetail {
	Details string `validate:"-"`
}

type User struct {
	Name         string     `validate:"required,max=60"`
	PreferedName string     `validate:"omitempty,max=60"`
	Sub          UserDetail
}

user := &User {
	Name: "",
}

// errs will contain a hierarchical list of errors
// using the StructErrors struct
// or nil if no errors exist
errs := validate.Struct(user)

// in this case 1 error Name is required
errs.Struct will be "User"
errs.StructErrors will be empty <-- fields that were structs
errs.Errors will have 1 error of type FieldError

NOTE: Anonymous Structs - they don't have names so expect the Struct name
within StructErrors to be blank.

Error Handling

The error can be used like so

fieldErr, _ := errs["Name"]
fieldErr.Field    // "Name"
fieldErr.ErrorTag // "required"

Both StructErrors and FieldError implement the Error interface but it's intended use is for development + debugging, not a production error message.

fieldErr.Error() // Field validation for "Name" failed on the "required" tag
errs.Error()
// Struct: User
// Field validation for "Name" failed on the "required" tag

Why not a better error message? because this library intends for you to handle your own error messages

Why should I handle my own errors? Many reasons, for us building an internationalized application I needed to know the field and what validation failed so that I could provide an error in the users specific language.

if fieldErr.Field == "Name" {
	switch fieldErr.ErrorTag
	case "required":
		return "Translated string based on field + error"
	default:
	return "Translated string based on field"
}

The hierarchical error structure is hard to work with sometimes.. Agreed Flatten function to the rescue! Flatten will return a map of FieldError's but the field name will be namespaced.

// if UserDetail Details field failed validation
Field will be "Sub.Details"

// for Name
Field will be "Name"

Custom Functions

Custom functions can be added

//Structure
func customFunc(top interface{}, current interface{}, field interface{}, param string) bool {

	if whatever {
		return false
	}

	return true
}

validate.AddFunction("custom tag name", customFunc)
// NOTES: using the same tag name as an existing function
//        will overwrite the existing one

Cross Field Validation

Cross Field Validation can be implemented, for example Start & End Date range validation

// NOTE: when calling validate.Struct(val) val will be the top level struct passed
//       into the function
//       when calling validate.FieldWithValue(val, field, tag) val will be
//       whatever you pass, struct, field...
//       when calling validate.Field(field, tag) val will be nil
//
// Because of the specific requirements and field names within each persons project that
// uses this library it is likely that custom functions will need to be created for your
// Cross Field Validation needs, however there are some build in Generic Cross Field validations,
// see Baked In Validators and Tags below

func isDateRangeValid(val interface{}, field interface{}, param string) bool {

	myStruct := val.(myStructType)

	if myStruct.Start.After(field.(time.Time)) {
		return false
	}

	return true
}

Multiple Validators

Multiple validators on a field will process in the order defined

type Test struct {
	Field `validate:"max=10,min=1"`
}

// max will be checked then min

Bad Validator definitions are not handled by the library

type Test struct {
	Field `validate:"min=10,max=0"`
}

// this definition of min max will never validate

Baked In Validators and Tags

NOTE: Baked In Cross field validation only compares fields on the same struct, if cross field + cross struct validation is needed your own custom validator should be implemented.

Here is a list of the current built in validators:

-
	Tells the validation to skip this struct field; this is particularily
	handy in ignoring embedded structs from being validated. (Usage: -)

|
	This is the 'or' operator allowing multiple validators to be used and
	accepted. (Usage: rbg|rgba) <-- this would allow either rgb or rgba
	colors to be accepted. This can also be combined with 'and' for example
	( Usage: omitempty,rgb|rgba)

structonly
	When a field that is a nest struct in encountered and contains this flag
	any validation on the nested struct such as "required" will be run, but
	none of the nested struct fields will be validated. This is usefull if
	inside of you program you know the struct will be valid, but need to
	verify it has been assigned.

omitempty
	Allows conitional validation, for example if a field is not set with
	a value (Determined by the required validator) then other validation
	such as min or max won't run, but if a value is set validation will run.
	(Usage: omitempty)

required
	This validates that the value is not the data types default value.
	For numbers ensures value is not zero. For strings ensures value is
	not "". For slices, arrays, and maps, ensures the length is not zero.
	(Usage: required)

len
	For numbers, max will ensure that the value is
	equal to the parameter given. For strings, it checks that
	the string length is exactly that number of characters. For slices,
	arrays, and maps, validates the number of items. (Usage: len=10)

max
	For numbers, max will ensure that the value is
	less than or equal to the parameter given. For strings, it checks
	that the string length is at most that number of characters. For
	slices, arrays, and maps, validates the number of items. (Usage: max=10)

min
	For numbers, min will ensure that the value is
	greater or equal to the parameter given. For strings, it checks that
	the string length is at least that number of characters. For slices,
	arrays, and maps, validates the number of items. (Usage: min=10)

gt
	For numbers, this will ensure that the value is greater than the
	parameter given. For strings, it checks that the string length
	is greater than that number of characters. For slices, arrays
	and maps it validates the number of items. (Usage: gt=10)
	For time.Time ensures the time value is greater than time.Now.UTC()
	(Usage: gt)

gte
	Same as 'min' above. Kept both to make terminology with 'len' easier
	(Usage: gte=10)
	For time.Time ensures the time value is greater than or equal to time.Now.UTC()
	(Usage: gte)

lt
	For numbers, this will ensure that the value is
	less than the parameter given. For strings, it checks
	that the string length is less than that number of characters.
	For slices, arrays, and maps it validates the number of items.
	(Usage: lt=10)
	For time.Time ensures the time value is less than time.Now.UTC()
	(Usage: lt)

lte
	Same as 'max' above. Kept both to make terminology with 'len' easier
	(Usage: lte=10)
	For time.Time ensures the time value is less than or equal to time.Now.UTC()
	(Usage: lte)

gtfield
	Only valid for Numbers and time.Time types, this will validate the field value
	against another fields value either within a struct or passed in field.
	usage examples are for validation of a Start and End date:
	Validation on End field using validate.Struct Usage(gtfield=Start)
	Validating by field validate.FieldWithValue(start, end, "gtfield")

gtefield
	Only valid for Numbers and time.Time types, this will validate the field value
	against another fields value either within a struct or passed in field.
	usage examples are for validation of a Start and End date:
	Validation on End field using validate.Struct Usage(gtefield=Start)
	Validating by field validate.FieldWithValue(start, end, "gtefield")

ltfield
	Only valid for Numbers and time.Time types, this will validate the field value
	against another fields value either within a struct or passed in field.
	usage examples are for validation of a Start and End date:
	Validation on End field using validate.Struct Usage(ltfield=Start)
	Validating by field validate.FieldWithValue(start, end, "ltfield")

ltefield
	Only valid for Numbers and time.Time types, this will validate the field value
	against another fields value either within a struct or passed in field.
	usage examples are for validation of a Start and End date:
	Validation on End field using validate.Struct Usage(ltefield=Start)
	Validating by field validate.FieldWithValue(start, end, "ltefield")

alpha
	This validates that a string value contains alpha characters only
	(Usage: alpha)

alphanum
	This validates that a string value contains alphanumeric characters only
	(Usage: alphanum)

numeric
	This validates that a string value contains a basic numeric value.
	basic excludes exponents etc...
	(Usage: numeric)

hexadecimal
	This validates that a string value contains a valid hexadecimal.
	(Usage: hexadecimal)

hexcolor
	This validates that a string value contains a valid hex color including
	hashtag (#)
	(Usage: hexcolor)

rgb
	This validates that a string value contains a valid rgb color
	(Usage: rgb)

rgba
	This validates that a string value contains a valid rgba color
	(Usage: rgba)

hsl
	This validates that a string value contains a valid hsl color
	(Usage: hsl)

hsla
	This validates that a string value contains a valid hsla color
	(Usage: hsla)

email
	This validates that a string value contains a valid email
	This may not conform to all possibilities of any rfc standard, but neither
	does any email provider accept all posibilities...
	(Usage: email)

url
	This validates that a string value contains a valid url
	This will accept any url the golang request uri accepts but must contain
	a schema for example http:// or rtmp://
	(Usage: url)

uri
	This validates that a string value contains a valid uri
	This will accept any uri the golang request uri accepts (Usage: uri)

base64
	This validates that a string value contains a valid base64 value.
	Although an empty string is valid base64 this will report an empty string
	as an error, if you wish to accept an empty string as valid you can use
	this with the omitempty tag. (Usage: base64)

Validator notes:

regex
	a regex validator won't be added because commas and = signs can be part of
	a regex which conflict with the validation definitions, although workarounds
	can be made, they take away from using pure regex's. Furthermore it's quick
	and dirty but the regex's become harder to maintain and are not reusable, so
	it's as much a programming philosiphy as anything.

	In place of this new validator functions should be created; a regex can be
	used within the validator function and even be precompiled for better efficiency
	within regexes.go.

	And the best reason, you can submit a pull request and we can keep on adding to the
	validation library of this package!

Panics

This package panics when bad input is provided, this is by design, bad code like that should not make it to production.

type Test struct {
	TestField string `validate:"nonexistantfunction=1"`
}

t := &Test{
	TestField: "Test"
}

validate.Struct(t) // this will panic

Index

Variables

var BakedInValidators = map[string]Func{
	"required":    hasValue,
	"len":         hasLengthOf,
	"min":         hasMinOf,
	"max":         hasMaxOf,
	"lt":          isLt,
	"lte":         isLte,
	"gt":          isGt,
	"gte":         isGte,
	"gtefield":    isGteField,
	"gtfield":     isGtField,
	"ltefield":    isLteField,
	"ltfield":     isLtField,
	"alpha":       isAlpha,
	"alphanum":    isAlphanum,
	"numeric":     isNumeric,
	"number":      isNumber,
	"hexadecimal": isHexadecimal,
	"hexcolor":    isHexcolor,
	"rgb":         isRgb,
	"rgba":        isRgba,
	"hsl":         isHsl,
	"hsla":        isHsla,
	"email":       isEmail,
	"url":         isURL,
	"uri":         isURI,
	"base64":      isBase64,
}

BakedInValidators is the default map of ValidationFunc you can add, remove or even replace items to suite your needs, or even disregard and use your own map if so desired.

type FieldError

type FieldError struct {
	Field string
	Tag   string
	Kind  reflect.Kind
	Type  reflect.Type
	Param string
	Value interface{}
}

FieldError contains a single field's validation error along with other properties that may be needed for error message creation

func (*FieldError) Error

func (e *FieldError) Error() string

This is intended for use in development + debugging and not intended to be a production error message. it also allows FieldError to be used as an Error interface

type Func

type Func func(top interface{}, current interface{}, f interface{}, param string) bool

Func accepts all values needed for file and cross field validation top = top level struct when validating by struct otherwise nil current = current level struct when validating by struct otherwise optional comparison value f = field value for validation param = parameter used in validation i.e. gt=0 param would be 0

type StructErrors

type StructErrors struct {
	// Name of the Struct
	Struct string
	// Struct Field Errors
	Errors map[string]*FieldError
	// Struct Fields of type struct and their errors
	// key = Field Name of current struct, but internally Struct will be the actual struct name unless anonymous struct, it will be blank
	StructErrors map[string]*StructErrors
}

StructErrors is hierarchical list of field and struct validation errors for a non hierarchical representation please see the Flatten method for StructErrors

func (*StructErrors) Error

func (e *StructErrors) Error() string

This is intended for use in development + debugging and not intended to be a production error message. it also allows StructErrors to be used as an Error interface

func (*StructErrors) Flatten

func (e *StructErrors) Flatten() map[string]*FieldError

Flatten flattens the StructErrors hierarchical structure into a flat namespace style field name for those that want/need it

type Validate

type Validate struct {
	// contains filtered or unexported fields
}

Validate implements the Validate Struct NOTE: Fields within are not thread safe and that is on purpose Functions and Tags should all be predifined before use, so subscribe to the philosiphy or make it thread safe on your end

func New

func New(tagName string, funcs map[string]Func) *Validate

New creates a new Validate instance for use.

func (*Validate) AddFunction

func (v *Validate) AddFunction(key string, f Func) error

AddFunction adds a validation Func to a Validate's map of validators denoted by the key NOTE: if the key already exists, it will get replaced.

func (*Validate) Field

func (v *Validate) Field(f interface{}, tag string) *FieldError

Field allows validation of a single field, still using tag style validation to check multiple errors

func (*Validate) FieldWithValue

func (v *Validate) FieldWithValue(val interface{}, f interface{}, tag string) *FieldError

FieldWithValue allows validation of a single field, possibly even against another fields value, still using tag style validation to check multiple errors

func (*Validate) SetTag

func (v *Validate) SetTag(tagName string)

SetTag sets tagName of the Validator to one of your choosing after creation perhaps to dodge a tag name conflict in a specific section of code

func (*Validate) Struct

func (v *Validate) Struct(s interface{}) *StructErrors

Struct validates a struct, even it's nested structs, and returns a struct containing the errors NOTE: Nested Arrays, or Maps of structs do not get validated only the Array or Map itself; the reason is that there is no good way to represent or report which struct within the array has the error, besides can validate the struct prior to adding it to the Array or Map.

Package Files

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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