Awesome

Checker

Checker is a Go library that helps you validate user input. It can be used to validate user input stored in a struct, or to validate individual pieces of input.

There are many validation libraries available, but I prefer to build my own tools and avoid pulling in unnecessary dependencies. That's why I created Checker, a simple validation library with no dependencies. It's easy to use and gets the job done.

Usage

To get started, install the Checker library with the following command:

go get github.com/cinar/checker

Next, you will need to import the library into your source file. You can do this by following the example below:

import (
    "github.com/cinar/checker"
)

Validating User Input Stored in a Struct

Checker can be used in two ways. The first way is to validate user input stored in a struct. To do this, you can list the checkers through the struct tag for each field. Here is an example:

type Person struct {
    Name string `checkers:"required"`
}

person := &Person{}

errors, valid := checker.Check(person)
if !valid {
    // Send the errors back to the user
}

Validating Individual User Input

If you do not want to validate user input stored in a struct, you can individually call the checker functions to validate the user input. Here is an example:

var name

err := checker.IsRequired(name)
if err != nil {
    // Send the result back to the user
}

Normalizers and Checkers

Checkers are used to check for problems in user input, while normalizers are used to transform user input into a preferred format. For example, a normalizer could be used to trim spaces from the beginning and end of a string, or to convert a string to title case.

I am not entirely happy with the decision to combine checkers and normalizers into a single library, but using them together can be useful. Normalizers and checkers can be mixed in any order when defining the validation steps for user data. For example, the trim normalizer can be used in conjunction with the required checker to first trim the user input and then check if the user provided the required information. Here is an example:

type Person struct {
    Name string `checkers:"trim required"`
}

Checkers Provided

This package currently provides the following checkers:

alphanumeric checks if the given string consists of only alphanumeric characters.
ascii checks if the given string consists of only ASCII characters.
cidr checker checks if the value is a valid CIDR notation IP address and prefix length.
credit-card checks if the given value is a valid credit card number.
digits checks if the given string consists of only digit characters.
email checks if the given string is an email address.
fqdn checks if the given string is a fully qualified domain name.
ip checks if the given value is an IP address.
ipv4 checks if the given value is an IPv4 address.
ipv6 checks if the given value is an IPv6 address.
isbn checks if the given value is a valid ISBN number.
luhn checks if the given number is valid based on the Luhn algorithm.
mac checks if the given value is a valid an IEEE 802 MAC-48, EUI-48, EUI-64, or a 20-octet IP over InfiniBand link-layer address.
max checks if the given value is less than the given maximum.
max-length checks if the length of the given value is less than the given maximum length.
min checks if the given value is greather than the given minimum.
min-length checks if the length of the given value is greather than the given minimum length.
regexp checks if the given string matches the regexp pattern.
required checks if the required value is provided.
same checks if the given value is equal to the value of the field with the given name.
url checks if the given value is a valid URL.

Normalizers Provided

This package currently provides the following normalizers. They can be mixed with the checkers when defining the validation steps for user data.

html-escape applies HTML escaping to special characters.
html-unescape applies HTML unescaping to special characters.
lower maps all Unicode letters in the given value to their lower case.
upper maps all Unicode letters in the given value to their upper case.
title maps the first letter of each word to their upper case.
trim removes the whitespaces at the beginning and at the end of the given value.
trim-left removes the whitespaces at the beginning of the given value.
trim-right removes the whitespaces at the end of the given value.
url-escape applies URL escaping to special characters.
url-unescape applies URL unescaping to special characters.

Custom Checkers

To define a custom checker, you need to create a new function with the following parameters:

func CustomChecker(value, parent reflect.Value) error {
    return nil
}

type MakeFunc You also need to create a make function that takes the checker configuration and returns a reference to the checker function.

func CustomMaker(params string) CheckFunc {
    return CustomChecker
}

Finally, you need to call the Register function to register your custom checker.

checker.Register("custom-checker", CustomMaker)

Once you have registered your custom checker, you can use it by simply specifying its name.

type User struct {
    Username string `checkers:"custom-checker"`
}

checker

import "github.com/cinar/checker"

Package checker is a Go library for validating user input through struct tags.

Index

Variables
func FailIfNoPanic(t *testing.T)
func IsASCII(value string) error
func IsAlphanumeric(value string) error
func IsAmexCreditCard(number string) error
func IsAnyCreditCard(number string) error
func IsCidr(value string) error
func IsDigits(value string) error
func IsDinersCreditCard(number string) error
func IsDiscoverCreditCard(number string) error
func IsEmail(email string) error
func IsFqdn(domain string) error
func IsIP(value string) error
func IsIPV4(value string) error
func IsIPV6(value string) error
func IsISBN(value string) error
func IsISBN10(value string) error
func IsISBN13(value string) error
func IsJcbCreditCard(number string) error
func IsLuhn(number string) error
func IsMac(value string) error
func IsMasterCardCreditCard(number string) error
func IsMax(value interface{}, max float64) error
func IsMaxLength(value interface{}, maxLength int) error
func IsMin(value interface{}, min float64) error
func IsMinLength(value interface{}, minLength int) error
func IsRequired(v interface{}) error
func IsURL(value string) error
func IsUnionPayCreditCard(number string) error
func IsVisaCreditCard(number string) error
func Register(name string, maker MakeFunc)
type CheckFunc
- func MakeRegexpChecker(expression string, invalidError error) CheckFunc
type Errors
- func Check(s interface{}) (Errors, bool)
type MakeFunc
- func MakeRegexpMaker(expression string, invalidError error) MakeFunc

Variables

<a name="ErrNotASCII"></a>ErrNotASCII indicates that the given string contains non-ASCII characters.

var ErrNotASCII = errors.New("please use standard English characters only")

<a name="ErrNotAlphanumeric"></a>ErrNotAlphanumeric indicates that the given string contains non-alphanumeric characters.

var ErrNotAlphanumeric = errors.New("please use only letters and numbers")

<a name="ErrNotCidr"></a>ErrNotCidr indicates that the given value is not a valid CIDR.

var ErrNotCidr = errors.New("please enter a valid CIDR")

<a name="ErrNotCreditCard"></a>ErrNotCreditCard indicates that the given value is not a valid credit card number.

var ErrNotCreditCard = errors.New("please enter a valid credit card number")

<a name="ErrNotDigits"></a>ErrNotDigits indicates that the given string contains non-digit characters.

var ErrNotDigits = errors.New("please enter a valid number")

<a name="ErrNotEmail"></a>ErrNotEmail indicates that the given string is not a valid email.

var ErrNotEmail = errors.New("please enter a valid email address")

<a name="ErrNotFqdn"></a>ErrNotFqdn indicates that the given string is not a valid FQDN.

var ErrNotFqdn = errors.New("please enter a valid domain name")

<a name="ErrNotIP"></a>ErrNotIP indicates that the given value is not an IP address.

var ErrNotIP = errors.New("please enter a valid IP address")

<a name="ErrNotIPV4"></a>ErrNotIPV4 indicates that the given value is not an IPv4 address.

var ErrNotIPV4 = errors.New("please enter a valid IPv4 address")

<a name="ErrNotIPV6"></a>ErrNotIPV6 indicates that the given value is not an IPv6 address.

var ErrNotIPV6 = errors.New("please enter a valid IPv6 address")

<a name="ErrNotISBN"></a>ErrNotISBN indicates that the given value is not a valid ISBN.

var ErrNotISBN = errors.New("please enter a valid ISBN number")

<a name="ErrNotLuhn"></a>ErrNotLuhn indicates that the given number is not valid based on the Luhn algorithm.

var ErrNotLuhn = errors.New("please enter a valid LUHN")

<a name="ErrNotMac"></a>ErrNotMac indicates that the given value is not an MAC address.

var ErrNotMac = errors.New("please enter a valid MAC address")

<a name="ErrNotMatch"></a>ErrNotMatch indicates that the given string does not match the regexp pattern.

var ErrNotMatch = errors.New("please enter a valid input")

<a name="ErrNotSame"></a>ErrNotSame indicates that the given two values are not equal to each other.

var ErrNotSame = errors.New("does not match the other")

<a name="ErrNotURL"></a>ErrNotURL indicates that the given value is not a valid URL.

var ErrNotURL = errors.New("please enter a valid URL")

<a name="ErrRequired"></a>ErrRequired indicates that the required value is missing.

var ErrRequired = errors.New("is required")

func FailIfNoPanic

func FailIfNoPanic(t *testing.T)

FailIfNoPanic fails if test didn't panic. Use this function with the defer.