validation

README

ozzo-validation

Description

ozzo-validation is a Go package that provides configurable and extensible data validation capabilities. It has the following features:

• use normal programming constructs rather than error-prone struct tags to specify how data should be validated.
• can validate data of different types, e.g., structs, strings, byte slices, slices, maps, arrays.
• can validate custom data types as long as they implement the Validatable interface.
• can validate data types that implement the sql.Valuer interface (e.g. sql.NullString).
• customizable and well-formatted validation errors.
• provide a rich set of validation rules right out of box.
• extremely easy to create and use custom validation rules.

Requirements

Go 1.8 or above.

Getting Started

The ozzo-validation package mainly includes a set of validation rules and two validation methods. You use validation rules to describe how a value should be considered valid, and you call either validation.Validate() or validation.ValidateStruct() to validate the value.

Installation

Run the following command to install the package:

go get github.com/go-ozzo/ozzo-validation
go get github.com/go-ozzo/ozzo-validation/is

Validating a Simple Value

For a simple value, such as a string or an integer, you may use validation.Validate() to validate it. For example,

package main

import (
	"fmt"

	"github.com/go-ozzo/ozzo-validation"
	"github.com/go-ozzo/ozzo-validation/is"
)

func main() {
	data := "example"
	err := validation.Validate(data,
		validation.Required,       // not empty
		validation.Length(5, 100), // length between 5 and 100
		is.URL,                    // is a valid URL
	)
	fmt.Println(err)
	// Output:
	// must be a valid URL
}

The method validation.Validate() will run through the rules in the order that they are listed. If a rule fails the validation, the method will return the corresponding error and skip the rest of the rules. The method will return nil if the value passes all validation rules.

Validating a Struct

For a struct value, you usually want to check if its fields are valid. For example, in a RESTful application, you may unmarshal the request payload into a struct and then validate the struct fields. If one or multiple fields are invalid, you may want to get an error describing which fields are invalid. You can use validation.ValidateStruct() to achieve this purpose. A single struct can have rules for multiple fields, and a field can be associated with multiple rules. For example,

package main

import (
	"fmt"
	"regexp"

	"github.com/go-ozzo/ozzo-validation"
	"github.com/go-ozzo/ozzo-validation/is"
)

type Address struct {
	Street string
	City   string
	State  string
	Zip    string
}

func (a Address) Validate() error {
	return validation.ValidateStruct(&a,
		// Street cannot be empty, and the length must between 5 and 50
		validation.Field(&a.Street, validation.Required, validation.Length(5, 50)),
		// City cannot be empty, and the length must between 5 and 50
		validation.Field(&a.City, validation.Required, validation.Length(5, 50)),
		// State cannot be empty, and must be a string consisting of two letters in upper case
		validation.Field(&a.State, validation.Required, validation.Match(regexp.MustCompile("^[A-Z]{2}$"))),
		// State cannot be empty, and must be a string consisting of five digits
		validation.Field(&a.Zip, validation.Required, validation.Match(regexp.MustCompile("^[0-9]{5}$"))),
	)
}

func main() {
	a := Address{
		Street: "123",
		City:   "Unknown",
		State:  "Virginia",
		Zip:    "12345",
	}

	err := a.Validate()
	fmt.Println(err)
	// Output:
	// Street: the length must be between 5 and 50; State: must be in a valid format.
}

Note that when calling validation.ValidateStruct to validate a struct, you should pass to the method a pointer to the struct instead of the struct itself. Similarly, when calling validation.Field to specify the rules for a struct field, you should use a pointer to the struct field.

When the struct validation is performed, the fields are validated in the order they are specified in ValidateStruct. And when each field is validated, its rules are also evaluated in the order they are associated with the field. If a rule fails, an error is recorded for that field, and the validation will continue with the next field.

Validation Errors

The validation.ValidateStruct method returns validation errors found in struct fields in terms of validation.Errors which is a map of fields and their corresponding errors. Nil is returned if validation passes.

By default, validation.Errors uses the struct tags named json to determine what names should be used to represent the invalid fields. The type also implements the json.Marshaler interface so that it can be marshaled into a proper JSON object. For example,

type Address struct {
	Street string `json:"street"`
	City   string `json:"city"`
	State  string `json:"state"`
	Zip    string `json:"zip"`
}

// ...perform validation here...

err := a.Validate()
b, _ := json.Marshal(err)
fmt.Println(string(b))
// Output:
// {"street":"the length must be between 5 and 50","state":"must be in a valid format"}

You may modify validation.ErrorTag to use a different struct tag name.

If you do not like the magic that ValidateStruct determines error keys based on struct field names or corresponding tag values, you may use the following alternative approach:

c := Customer{
	Name:  "Qiang Xue",
	Email: "q",
	Address: Address{
		State:  "Virginia",
	},
}

err := validation.Errors{
	"name": validation.Validate(c.Name, validation.Required, validation.Length(5, 20)),
	"email": validation.Validate(c.Name, validation.Required, is.Email),
	"zip": validation.Validate(c.Address.Zip, validation.Required, validation.Match(regexp.MustCompile("^[0-9]{5}$"))),
}.Filter()
fmt.Println(err)
// Output:
// email: must be a valid email address; zip: cannot be blank.

In the above example, we build a validation.Errors by a list of names and the corresponding validation results. At the end we call Errors.Filter() to remove from Errors all nils which correspond to those successful validation results. The method will return nil if Errors is empty.

The above approach is very flexible as it allows you to freely build up your validation error structure. You can use it to validate both struct and non-struct values. Compared to using ValidateStruct to validate a struct, it has the drawback that you have to redundantly specify the error keys while ValidateStruct can automatically find them out.

Internal Errors

Internal errors are different from validation errors in that internal errors are caused by malfunctioning code (e.g. a validator making a remote call to validate some data when the remote service is down) rather than the data being validated. When an internal error happens during data validation, you may allow the user to resubmit the same data to perform validation again, hoping the program resumes functioning. On the other hand, if data validation fails due to data error, the user should generally not resubmit the same data again.

To differentiate internal errors from validation errors, when an internal error occurs in a validator, wrap it into validation.InternalError by calling validation.NewInternalError(). The user of the validator can then check if a returned error is an internal error or not. For example,

if err := a.Validate(); err != nil {
	if e, ok := err.(validation.InternalError); ok {
		// an internal error happened
		fmt.Println(e.InternalError())
	}
}

Validatable Types

A type is validatable if it implements the validation.Validatable interface.

When validation.Validate is used to validate a validatable value, if it does not find any error with the given validation rules, it will further call the value's Validate() method.

Similarly, when validation.ValidateStruct is validating a struct field whose type is validatable, it will call the field's Validate method after it passes the listed rules.

In the following example, the Address field of Customer is validatable because Address implements validation.Validatable. Therefore, when validating a Customer struct with validation.ValidateStruct, validation will "dive" into the Address field.

type Customer struct {
	Name    string
	Gender  string
	Email   string
	Address Address
}

func (c Customer) Validate() error {
	return validation.ValidateStruct(&c,
		// Name cannot be empty, and the length must be between 5 and 20.
		validation.Field(&c.Name, validation.Required, validation.Length(5, 20)),
		// Gender is optional, and should be either "Female" or "Male".
		validation.Field(&c.Gender, validation.In("Female", "Male")),
		// Email cannot be empty and should be in a valid email format.
		validation.Field(&c.Email, validation.Required, is.Email),
		// Validate Address using its own validation rules
		validation.Field(&c.Address),
	)
}

c := Customer{
	Name:  "Qiang Xue",
	Email: "q",
	Address: Address{
		Street: "123 Main Street",
		City:   "Unknown",
		State:  "Virginia",
		Zip:    "12345",
	},
}

err := c.Validate()
fmt.Println(err)
// Output:
// Address: (State: must be in a valid format.); Email: must be a valid email address.

Sometimes, you may want to skip the invocation of a type's Validate method. To do so, simply associate a validation.Skip rule with the value being validated.

Maps/Slices/Arrays of Validatables

When validating an iterable (map, slice, or array), whose element type implements the validation.Validatable interface, the validation.Validate method will call the Validate method of every non-nil element. The validation errors of the elements will be returned as validation.Errors which maps the keys of the invalid elements to their corresponding validation errors. For example,

addresses := []Address{
	Address{State: "MD", Zip: "12345"},
	Address{Street: "123 Main St", City: "Vienna", State: "VA", Zip: "12345"},
	Address{City: "Unknown", State: "NC", Zip: "123"},
}
err := validation.Validate(addresses)
fmt.Println(err)
// Output:
// 0: (City: cannot be blank; Street: cannot be blank.); 2: (Street: cannot be blank; Zip: must be in a valid format.).

When using validation.ValidateStruct to validate a struct, the above validation procedure also applies to those struct fields which are map/slices/arrays of validatables.

Each

An other option is to use the validation.Each method. This method allows you to define the rules for the iterables within a struct.

type Customer struct {
    Name      string
    Emails    []string
}

func (c Customer) Validate() error {
    return validation.ValidateStruct(&c,
        // Name cannot be empty, and the length must be between 5 and 20.
		validation.Field(&c.Name, validation.Required, validation.Length(5, 20)),
		// Emails are optional, but if given must be valid.
		validation.Field(&c.Emails, validation.Each(is.Email)),
    )
}

c := Customer{
    Name:   "Qiang Xue",
    Emails: []Email{
        "valid@example.com",
        "invalid",
    },
}

err := c.Validate()
fmt.Println(err)
// Output:
// Emails: (1: must be a valid email address.).

Pointers

When a value being validated is a pointer, most validation rules will validate the actual value pointed to by the pointer. If the pointer is nil, these rules will skip the validation.

An exception is the validation.Required and validation.NotNil rules. When a pointer is nil, they will report a validation error.

Types Implementing sql.Valuer

If a data type implements the sql.Valuer interface (e.g. sql.NullString), the built-in validation rules will handle it properly. In particular, when a rule is validating such data, it will call the Value() method and validate the returned value instead.

Required vs. Not Nil

When validating input values, there are two different scenarios about checking if input values are provided or not.

In the first scenario, an input value is considered missing if it is not entered or it is entered as a zero value (e.g. an empty string, a zero integer). You can use the validation.Required rule in this case.

In the second scenario, an input value is considered missing only if it is not entered. A pointer field is usually used in this case so that you can detect if a value is entered or not by checking if the pointer is nil or not. You can use the validation.NotNil rule to ensure a value is entered (even if it is a zero value).

Embedded Structs

The validation.ValidateStruct method will properly validate a struct that contains embedded structs. In particular, the fields of an embedded struct are treated as if they belong directly to the containing struct. For example,

type Employee struct {
	Name string
}

func ()

type Manager struct {
	Employee
	Level int
}

m := Manager{}
err := validation.ValidateStruct(&m,
	validation.Field(&m.Name, validation.Required),
	validation.Field(&m.Level, validation.Required),
)
fmt.Println(err)
// Output:
// Level: cannot be blank; Name: cannot be blank.

In the above code, we use &m.Name to specify the validation of the Name field of the embedded struct Employee. And the validation error uses Name as the key for the error associated with the Name field as if Name a field directly belonging to Manager.

If Employee implements the validation.Validatable interface, we can also use the following code to validate Manager, which generates the same validation result:

func (e Employee) Validate() error {
	return validation.ValidateStruct(&e,
		validation.Field(&e.Name, validation.Required),
	)
}

err := validation.ValidateStruct(&m,
	validation.Field(&m.Employee),
	validation.Field(&m.Level, validation.Required),
)
fmt.Println(err)
// Output:
// Level: cannot be blank; Name: cannot be blank.

Built-in Validation Rules

The following rules are provided in the validation package:

• In(...interface{}): checks if a value can be found in the given list of values.
• Length(min, max int): checks if the length of a value is within the specified range. This rule should only be used for validating strings, slices, maps, and arrays.
• RuneLength(min, max int): checks if the length of a string is within the specified range. This rule is similar as Length except that when the value being validated is a string, it checks its rune length instead of byte length.
• Min(min interface{}) and Max(max interface{}): checks if a value is within the specified range. These two rules should only be used for validating int, uint, float and time.Time types.
• Match(*regexp.Regexp): checks if a value matches the specified regular expression. This rule should only be used for strings and byte slices.
• Date(layout string): checks if a string value is a date whose format is specified by the layout. By calling Min() and/or Max(), you can check additionally if the date is within the specified range.
• Required: checks if a value is not empty (neither nil nor zero).
• NotNil: checks if a pointer value is not nil. Non-pointer values are considered valid.
• NilOrNotEmpty: checks if a value is a nil pointer or a non-empty value. This differs from Required in that it treats a nil pointer as valid.
• Skip: this is a special rule used to indicate that all rules following it should be skipped (including the nested ones).
• MultipleOf: checks if the value is a multiple of the specified range.
• Each(rules ...Rule): checks the elements within an iterable (map/slice/array) with other rules.

The is sub-package provides a list of commonly used string validation rules that can be used to check if the format of a value satisfies certain requirements. Note that these rules only handle strings and byte slices and if a string or byte slice is empty, it is considered valid. You may use a Required rule to ensure a value is not empty. Below is the whole list of the rules provided by the is package:

• Email: validates if a string is an email or not
• URL: validates if a string is a valid URL
• RequestURL: validates if a string is a valid request URL
• RequestURI: validates if a string is a valid request URI
• Alpha: validates if a string contains English letters only (a-zA-Z)
• Digit: validates if a string contains digits only (0-9)
• Alphanumeric: validates if a string contains English letters and digits only (a-zA-Z0-9)
• UTFLetter: validates if a string contains unicode letters only
• UTFDigit: validates if a string contains unicode decimal digits only
• UTFLetterNumeric: validates if a string contains unicode letters and numbers only
• UTFNumeric: validates if a string contains unicode number characters (category N) only
• LowerCase: validates if a string contains lower case unicode letters only
• UpperCase: validates if a string contains upper case unicode letters only
• Hexadecimal: validates if a string is a valid hexadecimal number
• HexColor: validates if a string is a valid hexadecimal color code
• RGBColor: validates if a string is a valid RGB color in the form of rgb(R, G, B)
• Int: validates if a string is a valid integer number
• Float: validates if a string is a floating point number
• UUIDv3: validates if a string is a valid version 3 UUID
• UUIDv4: validates if a string is a valid version 4 UUID
• UUIDv5: validates if a string is a valid version 5 UUID
• UUID: validates if a string is a valid UUID
• CreditCard: validates if a string is a valid credit card number
• ISBN10: validates if a string is an ISBN version 10
• ISBN13: validates if a string is an ISBN version 13
• ISBN: validates if a string is an ISBN (either version 10 or 13)
• JSON: validates if a string is in valid JSON format
• ASCII: validates if a string contains ASCII characters only
• PrintableASCII: validates if a string contains printable ASCII characters only
• Multibyte: validates if a string contains multibyte characters
• FullWidth: validates if a string contains full-width characters
• HalfWidth: validates if a string contains half-width characters
• VariableWidth: validates if a string contains both full-width and half-width characters
• Base64: validates if a string is encoded in Base64
• DataURI: validates if a string is a valid base64-encoded data URI
• E164: validates if a string is a valid E164 phone number (+19251232233)
• CountryCode2: validates if a string is a valid ISO3166 Alpha 2 country code
• CountryCode3: validates if a string is a valid ISO3166 Alpha 3 country code
• DialString: validates if a string is a valid dial string that can be passed to Dial()
• MAC: validates if a string is a MAC address
• IP: validates if a string is a valid IP address (either version 4 or 6)
• IPv4: validates if a string is a valid version 4 IP address
• IPv6: validates if a string is a valid version 6 IP address
• Subdomain: validates if a string is valid subdomain
• Domain: validates if a string is valid domain
• DNSName: validates if a string is valid DNS name
• Host: validates if a string is a valid IP (both v4 and v6) or a valid DNS name
• Port: validates if a string is a valid port number
• MongoID: validates if a string is a valid Mongo ID
• Latitude: validates if a string is a valid latitude
• Longitude: validates if a string is a valid longitude
• SSN: validates if a string is a social security number (SSN)
• Semver: validates if a string is a valid semantic version

Customizing Error Messages

All built-in validation rules allow you to customize error messages. To do so, simply call the Error() method of the rules. For example,

data := "2123"
err := validation.Validate(data,
	validation.Required.Error("is required"),
	validation.Match(regexp.MustCompile("^[0-9]{5}$")).Error("must be a string with five digits"),
)
fmt.Println(err)
// Output:
// must be a string with five digits

Creating Custom Rules

Creating a custom rule is as simple as implementing the validation.Rule interface. The interface contains a single method as shown below, which should validate the value and return the validation error, if any:

// Validate validates a value and returns an error if validation fails.
Validate(value interface{}) error

If you already have a function with the same signature as shown above, you can call validation.By() to turn it into a validation rule. For example,

func checkAbc(value interface{}) error {
	s, _ := value.(string)
	if s != "abc" {
		return errors.New("must be abc")
	}
	return nil
}

err := validation.Validate("xyz", validation.By(checkAbc))
fmt.Println(err)
// Output: must be abc

If your validation function takes additional parameters, you can use the following closure trick:

func stringEquals(str string) validation.RuleFunc {
	return func(value interface{}) error {
		s, _ := value.(string)
        if s != str {
            return errors.New("unexpected string")
        }
        return nil
    }
}

err := validation.Validate("xyz", validation.By(stringEquals("abc")))
fmt.Println(err)
// Output: unexpected string

Rule Groups

When a combination of several rules are used in multiple places, you may use the following trick to create a rule group so that your code is more maintainable.

var NameRule = []validation.Rule{
	validation.Required,
	validation.Length(5, 20),
}

type User struct {
	FirstName string
	LastName  string
}

func (u User) Validate() error {
	return validation.ValidateStruct(&u,
		validation.Field(&u.FirstName, NameRule...),
		validation.Field(&u.LastName, NameRule...),
	)
}

In the above example, we create a rule group NameRule which consists of two validation rules. We then use this rule group to validate both FirstName and LastName.

Credits

The is sub-package wraps the excellent validators provided by the govalidator package.

Documentation

Overview

Package validation provides configurable and extensible rules for validating data of various types.

Example

c := Customer{
	Name:  "Qiang Xue",
	Email: "q",
	Address: Address{
		Street: "123 Main Street",
		City:   "Unknown",
		State:  "Virginia",
		Zip:    "12345",
	},
}

err := c.Validate()
fmt.Println(err)

Output:

Address: (State: must be in a valid format.); Email: must be a valid email address.

Example (Five)

type Employee struct {
	Name string
}

type Manager struct {
	Employee
	Level int
}

m := Manager{}
err := validation.ValidateStruct(&m,
	validation.Field(&m.Name, validation.Required),
	validation.Field(&m.Level, validation.Required),
)
fmt.Println(err)

Output:

Level: cannot be blank; Name: cannot be blank.

Example (Four)

c := Customer{
	Name:  "Qiang Xue",
	Email: "q",
	Address: Address{
		State: "Virginia",
	},
}

err := validation.Errors{
	"name":  validation.Validate(c.Name, validation.Required, validation.Length(5, 20)),
	"email": validation.Validate(c.Name, validation.Required, is.Email),
	"zip":   validation.Validate(c.Address.Zip, validation.Required, validation.Match(regexp.MustCompile("^[0-9]{5}$"))),
}.Filter()
fmt.Println(err)

Output:

email: must be a valid email address; zip: cannot be blank.

Example (Second)

data := "example"
err := validation.Validate(data,
	validation.Required,       // not empty
	validation.Length(5, 100), // length between 5 and 100
	is.URL,                    // is a valid URL
)
fmt.Println(err)

Output:

must be a valid URL

Example (Third)

addresses := []Address{
	{State: "MD", Zip: "12345"},
	{Street: "123 Main St", City: "Vienna", State: "VA", Zip: "12345"},
	{City: "Unknown", State: "NC", Zip: "123"},
}
err := validation.Validate(addresses)
fmt.Println(err)

Output:

0: (City: cannot be blank; Street: cannot be blank.); 2: (Street: cannot be blank; Zip: must be in a valid format.).

Index

• Variables
• func EnsureString(value interface{}) (string, error)
• func Indirect(value interface{}) (interface{}, bool)
• func IsEmpty(value interface{}) bool
• func LengthOfValue(value interface{}) (int, error)
• func MultipleOf(threshold interface{}) *multipleOfRule
• func StringOrBytes(value interface{}) (isString bool, str string, isBytes bool, bs []byte)
• func ToFloat(value interface{}) (float64, error)
• func ToInt(value interface{}) (int64, error)
• func ToUint(value interface{}) (uint64, error)
• func Validate(value interface{}, rules ...Rule) error
• func ValidateStruct(structPtr interface{}, fields ...*FieldRules) error
• type DateRule
  • func Date(layout string) *DateRule
  • func (r *DateRule) Error(message string) *DateRule
  • func (r *DateRule) Max(max time.Time) *DateRule
  • func (r *DateRule) Min(min time.Time) *DateRule
  • func (r *DateRule) RangeError(message string) *DateRule
  • func (r *DateRule) Validate(value interface{}) error
• type EachRule
  • func Each(rules ...Rule) *EachRule
  • func (r *EachRule) Validate(value interface{}) error
• type ErrFieldNotFound
  • func (e ErrFieldNotFound) Error() string
• type ErrFieldPointer
  • func (e ErrFieldPointer) Error() string
• type Errors
  • func (es Errors) Error() string
  • func (es Errors) Filter() error
  • func (es Errors) MarshalJSON() ([]byte, error)
• type FieldRules
  • func Field(fieldPtr interface{}, rules ...Rule) *FieldRules
• type InRule
  • func In(values ...interface{}) *InRule
  • func (r *InRule) Error(message string) *InRule
  • func (r *InRule) Validate(value interface{}) error
• type InternalError
  • func NewInternalError(err error) InternalError
• type LengthRule
  • func Length(min, max int) *LengthRule
  • func RuneLength(min, max int) *LengthRule
  • func (v *LengthRule) Error(message string) *LengthRule
  • func (v *LengthRule) Validate(value interface{}) error
• type MatchRule
  • func Match(re *regexp.Regexp) *MatchRule
  • func (v *MatchRule) Error(message string) *MatchRule
  • func (v *MatchRule) Validate(value interface{}) error
• type NotInRule
  • func NotIn(values ...interface{}) *NotInRule
  • func (r *NotInRule) Error(message string) *NotInRule
  • func (r *NotInRule) Validate(value interface{}) error
• type Rule
  • func By(f RuleFunc) Rule
• type RuleFunc
• type StringRule
  • func NewStringRule(validator stringValidator, message string) *StringRule
  • func (v *StringRule) Error(message string) *StringRule
  • func (v *StringRule) Validate(value interface{}) error
• type ThresholdRule
  • func Max(max interface{}) *ThresholdRule
  • func Min(min interface{}) *ThresholdRule
  • func (r *ThresholdRule) Error(message string) *ThresholdRule
  • func (r *ThresholdRule) Exclusive() *ThresholdRule
  • func (r *ThresholdRule) Validate(value interface{}) error
• type Validatable

Examples

• Package
• Package (Five)
• Package (Four)
• Package (Second)
• Package (Third)

Variables

var (
	// ErrorTag is the struct tag name used to customize the error field name for a struct field.
	ErrorTag = "json"

	// Skip is a special validation rule that indicates all rules following it should be skipped.
	Skip = &skipRule{}
)

var (
	// ErrStructPointer is the error that a struct being validated is not specified as a pointer.
	ErrStructPointer = errors.New("only a pointer to a struct can be validated")
)

var NilOrNotEmpty = &requiredRule{message: "cannot be blank", skipNil: true}

NilOrNotEmpty checks if a value is a nil pointer or a value that is not empty. NilOrNotEmpty differs from Required in that it treats a nil pointer as valid.

var NotNil = &notNilRule{message: "is required"}

NotNil is a validation rule that checks if a value is not nil. NotNil only handles types including interface, pointer, slice, and map. All other types are considered valid.

var Required = &requiredRule{message: "cannot be blank", skipNil: false}

Required is a validation rule that checks if a value is not empty. A value is considered not empty if - integer, float: not zero - bool: true - string, array, slice, map: len() > 0 - interface, pointer: not nil and the referenced value is not empty - any other types

Functions

func EnsureString

func EnsureString(value interface{}) (string, error)

EnsureString ensures the given value is a string. If the value is a byte slice, it will be typecast into a string. An error is returned otherwise.

func Indirect

func Indirect(value interface{}) (interface{}, bool)

Indirect returns the value that the given interface or pointer references to. If the value implements driver.Valuer, it will deal with the value returned by the Value() method instead. A boolean value is also returned to indicate if the value is nil or not (only applicable to interface, pointer, map, and slice). If the value is neither an interface nor a pointer, it will be returned back.

func IsEmpty

func IsEmpty(value interface{}) bool

IsEmpty checks if a value is empty or not. A value is considered empty if - integer, float: zero - bool: false - string, array: len() == 0 - slice, map: nil or len() == 0 - interface, pointer: nil or the referenced value is empty

func LengthOfValue

func LengthOfValue(value interface{}) (int, error)

LengthOfValue returns the length of a value that is a string, slice, map, or array. An error is returned for all other types.

func MultipleOf

func MultipleOf(threshold interface{}) *multipleOfRule

func StringOrBytes

func StringOrBytes(value interface{}) (isString bool, str string, isBytes bool, bs []byte)

StringOrBytes typecasts a value into a string or byte slice. Boolean flags are returned to indicate if the typecasting succeeds or not.

func ToFloat

func ToFloat(value interface{}) (float64, error)

ToFloat converts the given value to a float64. An error is returned for all incompatible types.

func ToInt

func ToInt(value interface{}) (int64, error)

ToInt converts the given value to an int64. An error is returned for all incompatible types.

func ToUint

func ToUint(value interface{}) (uint64, error)

ToUint converts the given value to an uint64. An error is returned for all incompatible types.

func Validate

func Validate(value interface{}, rules ...Rule) error

Validate validates the given value and returns the validation error, if any.

Validate performs validation using the following steps: - validate the value against the rules passed in as parameters - if the value is a map and the map values implement `Validatable`, call `Validate` of every map value - if the value is a slice or array whose values implement `Validatable`, call `Validate` of every element

func ValidateStruct

func ValidateStruct(structPtr interface{}, fields ...*FieldRules) error

ValidateStruct validates a struct by checking the specified struct fields against the corresponding validation rules. Note that the struct being validated must be specified as a pointer to it. If the pointer is nil, it is considered valid. Use Field() to specify struct fields that need to be validated. Each Field() call specifies a single field which should be specified as a pointer to the field. A field can be associated with multiple rules. For example,

value := struct {
    Name  string
    Value string
}{"name", "demo"}
err := validation.ValidateStruct(&value,
     validation.Field(&a.Name, validation.Required),
     validation.Field(&a.Value, validation.Required, validation.Length(5, 10)),
)
fmt.Println(err)
// Value: the length must be between 5 and 10.

An error will be returned if validation fails.

Types

type DateRule

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

func Date

func Date(layout string) *DateRule

Date returns a validation rule that checks if a string value is in a format that can be parsed into a date. The format of the date should be specified as the layout parameter which accepts the same value as that for time.Parse. For example,

validation.Date(time.ANSIC)
validation.Date("02 Jan 06 15:04 MST")
validation.Date("2006-01-02")

By calling Min() and/or Max(), you can let the Date rule to check if a parsed date value is within the specified date range.

An empty value is considered valid. Use the Required rule to make sure a value is not empty.

func (*DateRule) Error

func (r *DateRule) Error(message string) *DateRule

Error sets the error message that is used when the value being validated is not a valid date.

func (*DateRule) Max

func (r *DateRule) Max(max time.Time) *DateRule

Max sets the maximum date range. A zero value means skipping the maximum range validation.

func (*DateRule) Min

func (r *DateRule) Min(min time.Time) *DateRule

Min sets the minimum date range. A zero value means skipping the minimum range validation.

func (*DateRule) RangeError

func (r *DateRule) RangeError(message string) *DateRule

RangeError sets the error message that is used when the value being validated is out of the specified Min/Max date range.

func (*DateRule) Validate

func (r *DateRule) Validate(value interface{}) error

Validate checks if the given value is a valid date.

type EachRule

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

func Each

func Each(rules ...Rule) *EachRule

Each returns a validation rule that loops through an iterable (map, slice or array) and validates each value inside with the provided rules. An empty iterable is considered valid. Use the Required rule to make sure the iterable is not empty.

func (*EachRule) Validate

func (r *EachRule) Validate(value interface{}) error

Loops through the given iterable and calls the Ozzo Validate() method for each value.

type ErrFieldNotFound

type ErrFieldNotFound int

ErrFieldNotFound is the error that a field cannot be found in the struct.

func (ErrFieldNotFound) Error

func (e ErrFieldNotFound) Error() string

Error returns the error string of ErrFieldNotFound.

type ErrFieldPointer

type ErrFieldPointer int

ErrFieldPointer is the error that a field is not specified as a pointer.

func (ErrFieldPointer) Error

func (e ErrFieldPointer) Error() string

Error returns the error string of ErrFieldPointer.

type Errors

type Errors map[string]error

Errors represents the validation errors that are indexed by struct field names, map or slice keys.

func (Errors) Error

func (es Errors) Error() string

Error returns the error string of Errors.

func (Errors) Filter

func (es Errors) Filter() error

Filter removes all nils from Errors and returns back the updated Errors as an error. If the length of Errors becomes 0, it will return nil.

func (Errors) MarshalJSON

func (es Errors) MarshalJSON() ([]byte, error)

MarshalJSON converts the Errors into a valid JSON.

type FieldRules

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

FieldRules represents a rule set associated with a struct field.

func Field

func Field(fieldPtr interface{}, rules ...Rule) *FieldRules

Field specifies a struct field and the corresponding validation rules. The struct field must be specified as a pointer to it.

type InRule

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

func In

func In(values ...interface{}) *InRule

In returns a validation rule that checks if a value can be found in the given list of values. Note that the value being checked and the possible range of values must be of the same type. An empty value is considered valid. Use the Required rule to make sure a value is not empty.

func (*InRule) Error

func (r *InRule) Error(message string) *InRule

Error sets the error message for the rule.

func (*InRule) Validate

func (r *InRule) Validate(value interface{}) error

Validate checks if the given value is valid or not.

type InternalError

type InternalError interface {
	error
	InternalError() error
}

InternalError represents an error that should NOT be treated as a validation error.

func NewInternalError

func NewInternalError(err error) InternalError

NewInternalError wraps a given error into an InternalError.

type LengthRule

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

func Length

func Length(min, max int) *LengthRule

Length returns a validation rule that checks if a value's length is within the specified range. If max is 0, it means there is no upper bound for the length. This rule should only be used for validating strings, slices, maps, and arrays. An empty value is considered valid. Use the Required rule to make sure a value is not empty.

func RuneLength

func RuneLength(min, max int) *LengthRule

RuneLength returns a validation rule that checks if a string's rune length is within the specified range. If max is 0, it means there is no upper bound for the length. This rule should only be used for validating strings, slices, maps, and arrays. An empty value is considered valid. Use the Required rule to make sure a value is not empty. If the value being validated is not a string, the rule works the same as Length.

func (*LengthRule) Error

func (v *LengthRule) Error(message string) *LengthRule

Error sets the error message for the rule.

func (*LengthRule) Validate

func (v *LengthRule) Validate(value interface{}) error

Validate checks if the given value is valid or not.

type MatchRule

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

func Match

func Match(re *regexp.Regexp) *MatchRule

Match returns a validation rule that checks if a value matches the specified regular expression. This rule should only be used for validating strings and byte slices, or a validation error will be reported. An empty value is considered valid. Use the Required rule to make sure a value is not empty.

func (*MatchRule) Error

func (v *MatchRule) Error(message string) *MatchRule

Error sets the error message for the rule.

func (*MatchRule) Validate

func (v *MatchRule) Validate(value interface{}) error

Validate checks if the given value is valid or not.

type NotInRule

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

func NotIn

func NotIn(values ...interface{}) *NotInRule

NotIn returns a validation rule that checks if a value os absent from, the given list of values. Note that the value being checked and the possible range of values must be of the same type. An empty value is considered valid. Use the Required rule to make sure a value is not empty.

func (*NotInRule) Error

func (r *NotInRule) Error(message string) *NotInRule

Error sets the error message for the rule.

func (*NotInRule) Validate

func (r *NotInRule) Validate(value interface{}) error

Validate checks if the given value is valid or not.

type Rule

type Rule interface {
	// Validate validates a value and returns a value if validation fails.
	Validate(value interface{}) error
}

Rule represents a validation rule.

func By

func By(f RuleFunc) Rule

By wraps a RuleFunc into a Rule.

type RuleFunc

type RuleFunc func(value interface{}) error

RuleFunc represents a validator function. You may wrap it as a Rule by calling By().

type StringRule

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

StringRule is a rule that checks a string variable using a specified stringValidator.

func NewStringRule

func NewStringRule(validator stringValidator, message string) *StringRule

NewStringRule creates a new validation rule using a function that takes a string value and returns a bool. The rule returned will use the function to check if a given string or byte slice is valid or not. An empty value is considered to be valid. Please use the Required rule to make sure a value is not empty.

func (*StringRule) Error

func (v *StringRule) Error(message string) *StringRule

Error sets the error message for the rule.

func (*StringRule) Validate

func (v *StringRule) Validate(value interface{}) error

Validate checks if the given value is valid or not.

type ThresholdRule

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

func Max

func Max(max interface{}) *ThresholdRule

Max is a validation rule that checks if a value is less or equal than the specified value. By calling Exclusive, the rule will check if the value is strictly less than the specified value. Note that the value being checked and the threshold value must be of the same type. Only int, uint, float and time.Time types are supported. An empty value is considered valid. Please use the Required rule to make sure a value is not empty.

func Min

func Min(min interface{}) *ThresholdRule

Min is a validation rule that checks if a value is greater or equal than the specified value. By calling Exclusive, the rule will check if the value is strictly greater than the specified value. Note that the value being checked and the threshold value must be of the same type. Only int, uint, float and time.Time types are supported. An empty value is considered valid. Please use the Required rule to make sure a value is not empty.

func (*ThresholdRule) Error

func (r *ThresholdRule) Error(message string) *ThresholdRule

Error sets the error message for the rule.

func (*ThresholdRule) Exclusive

func (r *ThresholdRule) Exclusive() *ThresholdRule

Exclusive sets the comparison to exclude the boundary value.

func (*ThresholdRule) Validate

func (r *ThresholdRule) Validate(value interface{}) error

Validate checks if the given value is valid or not.

type Validatable

type Validatable interface {
	// Validate validates the data and returns an error if validation fails.
	Validate() error
}

Validatable is the interface indicating the type implementing it supports data validation.