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# v2

```go
import "github.com/cinar/checker/v2"
```

Package v2 Checker is a Go library for validating user input through checker rules provided in struct tags.

## Index

- [Constants](<#constants>)
- [Variables](<#variables>)
- [func Check\[T any\]\(value T, checks ...CheckFunc\[T\]\) \(T, error\)](<#Check>)
- [func CheckStruct\(st any\) \(map\[string\]error, bool\)](<#CheckStruct>)
- [func CheckWithConfig\[T any\]\(value T, config string\) \(T, error\)](<#CheckWithConfig>)
- [func HTMLEscape\(value string\) \(string, error\)](<#HTMLEscape>)
- [func HTMLUnescape\(value string\) \(string, error\)](<#HTMLUnescape>)
- [func IsASCII\(value string\) \(string, error\)](<#IsASCII>)
- [func IsAlphanumeric\(value string\) \(string, error\)](<#IsAlphanumeric>)
- [func IsAmexCreditCard\(number string\) \(string, error\)](<#IsAmexCreditCard>)
- [func IsAnyCreditCard\(number string\) \(string, error\)](<#IsAnyCreditCard>)
- [func IsCIDR\(value string\) \(string, error\)](<#IsCIDR>)
- [func IsDigits\(value string\) \(string, error\)](<#IsDigits>)
- [func IsDinersCreditCard\(number string\) \(string, error\)](<#IsDinersCreditCard>)
- [func IsDiscoverCreditCard\(number string\) \(string, error\)](<#IsDiscoverCreditCard>)
- [func IsEmail\(value string\) \(string, error\)](<#IsEmail>)
- [func IsFQDN\(value string\) \(string, error\)](<#IsFQDN>)
- [func IsGte\[T cmp.Ordered\]\(value, n T\) \(T, error\)](<#IsGte>)
- [func IsHex\(value string\) \(string, error\)](<#IsHex>)
- [func IsIP\(value string\) \(string, error\)](<#IsIP>)
- [func IsIPv4\(value string\) \(string, error\)](<#IsIPv4>)
- [func IsIPv6\(value string\) \(string, error\)](<#IsIPv6>)
- [func IsISBN\(value string\) \(string, error\)](<#IsISBN>)
- [func IsJcbCreditCard\(number string\) \(string, error\)](<#IsJcbCreditCard>)
- [func IsLUHN\(value string\) \(string, error\)](<#IsLUHN>)
- [func IsLte\[T cmp.Ordered\]\(value, n T\) \(T, error\)](<#IsLte>)
- [func IsMAC\(value string\) \(string, error\)](<#IsMAC>)
- [func IsMasterCardCreditCard\(number string\) \(string, error\)](<#IsMasterCardCreditCard>)
- [func IsRegexp\(expression, value string\) \(string, error\)](<#IsRegexp>)
- [func IsTime\(params, value string\) \(string, error\)](<#IsTime>)
- [func IsURL\(value string\) \(string, error\)](<#IsURL>)
- [func IsUnionPayCreditCard\(number string\) \(string, error\)](<#IsUnionPayCreditCard>)
- [func IsVisaCreditCard\(number string\) \(string, error\)](<#IsVisaCreditCard>)
- [func Lower\(value string\) \(string, error\)](<#Lower>)
- [func ReflectCheckWithConfig\(value reflect.Value, config string\) \(reflect.Value, error\)](<#ReflectCheckWithConfig>)
- [func RegisterLocale\(locale string, messages map\[string\]string\)](<#RegisterLocale>)
- [func RegisterMaker\(name string, maker MakeCheckFunc\)](<#RegisterMaker>)
- [func Required\[T any\]\(value T\) \(T, error\)](<#Required>)
- [func Title\(value string\) \(string, error\)](<#Title>)
- [func TrimLeft\(value string\) \(string, error\)](<#TrimLeft>)
- [func TrimRight\(value string\) \(string, error\)](<#TrimRight>)
- [func TrimSpace\(value string\) \(string, error\)](<#TrimSpace>)
- [func URLEscape\(value string\) \(string, error\)](<#URLEscape>)
- [func URLUnescape\(value string\) \(string, error\)](<#URLUnescape>)
- [func Upper\(value string\) \(string, error\)](<#Upper>)
- [type CheckError](<#CheckError>)
  - [func NewCheckError\(code string\) \*CheckError](<#NewCheckError>)
  - [func NewCheckErrorWithData\(code string, data map\[string\]interface\{\}\) \*CheckError](<#NewCheckErrorWithData>)
  - [func \(c \*CheckError\) Error\(\) string](<#CheckError.Error>)
  - [func \(c \*CheckError\) ErrorWithLocale\(locale string\) string](<#CheckError.ErrorWithLocale>)
  - [func \(c \*CheckError\) Is\(target error\) bool](<#CheckError.Is>)
- [type CheckFunc](<#CheckFunc>)
  - [func MakeRegexpChecker\(expression string, invalidError error\) CheckFunc\[reflect.Value\]](<#MakeRegexpChecker>)
  - [func MaxLen\[T any\]\(n int\) CheckFunc\[T\]](<#MaxLen>)
  - [func MinLen\[T any\]\(n int\) CheckFunc\[T\]](<#MinLen>)
- [type MakeCheckFunc](<#MakeCheckFunc>)


## Constants

<a name="DefaultLocale"></a>

```go
const (
    // DefaultLocale is the default locale.
    DefaultLocale = locales.EnUS
)
```

## Variables

<a name="ErrGte"></a>

```go
var (
    // ErrGte indicates that the value is not greater than or equal to the given value.
    ErrGte = NewCheckError("NOT_GTE")
)
```

<a name="ErrLte"></a>

```go
var (
    // ErrLte indicates that the value is not less than or equal to the given value.
    ErrLte = NewCheckError("NOT_LTE")
)
```

<a name="ErrMaxLen"></a>

```go
var (
    // ErrMaxLen indicates that the value's length is greater than the specified maximum.
    ErrMaxLen = NewCheckError("NOT_MAX_LEN")
)
```

<a name="ErrMinLen"></a>

```go
var (
    // ErrMinLen indicates that the value's length is less than the specified minimum.
    ErrMinLen = NewCheckError("NOT_MIN_LEN")
)
```

<a name="ErrNotASCII"></a>

```go
var (
    // ErrNotASCII indicates that the given string contains non-ASCII characters.
    ErrNotASCII = NewCheckError("NOT_ASCII")
)
```

<a name="ErrNotAlphanumeric"></a>

```go
var (
    // ErrNotAlphanumeric indicates that the given string contains non-alphanumeric characters.
    ErrNotAlphanumeric = NewCheckError("NOT_ALPHANUMERIC")
)
```

<a name="ErrNotCIDR"></a>

```go
var (
    // ErrNotCIDR indicates that the given value is not a valid CIDR.
    ErrNotCIDR = NewCheckError("NOT_CIDR")
)
```

<a name="ErrNotCreditCard"></a>

```go
var (
    // ErrNotCreditCard indicates that the given value is not a valid credit card number.
    ErrNotCreditCard = NewCheckError("NOT_CREDIT_CARD")
)
```

<a name="ErrNotDigits"></a>

```go
var (
    // ErrNotDigits indicates that the given value is not a valid digits string.
    ErrNotDigits = NewCheckError("NOT_DIGITS")
)
```

<a name="ErrNotEmail"></a>

```go
var (
    // ErrNotEmail indicates that the given value is not a valid email address.
    ErrNotEmail = NewCheckError("NOT_EMAIL")
)
```

<a name="ErrNotFQDN"></a>

```go
var (
    // ErrNotFQDN indicates that the given value is not a valid FQDN.
    ErrNotFQDN = NewCheckError("FQDN")
)
```

<a name="ErrNotHex"></a>

```go
var (
    // ErrNotHex indicates that the given string contains hex characters.
    ErrNotHex = NewCheckError("NOT_HEX")
)
```

<a name="ErrNotIP"></a>

```go
var (
    // ErrNotIP indicates that the given value is not a valid IP address.
    ErrNotIP = NewCheckError("NOT_IP")
)
```

<a name="ErrNotIPv4"></a>

```go
var (
    // ErrNotIPv4 indicates that the given value is not a valid IPv4 address.
    ErrNotIPv4 = NewCheckError("NOT_IPV4")
)
```

<a name="ErrNotIPv6"></a>

```go
var (
    // ErrNotIPv6 indicates that the given value is not a valid IPv6 address.
    ErrNotIPv6 = NewCheckError("NOT_IPV6")
)
```

<a name="ErrNotISBN"></a>

```go
var (
    // ErrNotISBN indicates that the given value is not a valid ISBN.
    ErrNotISBN = NewCheckError("NOT_ISBN")
)
```

<a name="ErrNotLUHN"></a>

```go
var (
    // ErrNotLUHN indicates that the given value is not a valid LUHN number.
    ErrNotLUHN = NewCheckError("NOT_LUHN")
)
```

<a name="ErrNotMAC"></a>

```go
var (
    // ErrNotMAC indicates that the given value is not a valid MAC address.
    ErrNotMAC = NewCheckError("NOT_MAC")
)
```

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

```go
var ErrNotMatch = NewCheckError("REGEXP")
```

<a name="ErrNotURL"></a>

```go
var (
    // ErrNotURL indicates that the given value is not a valid URL.
    ErrNotURL = NewCheckError("NOT_URL")
)
```

<a name="ErrRequired"></a>

```go
var (
    // ErrRequired indicates that a required value was missing.
    ErrRequired = NewCheckError("REQUIRED")
)
```

<a name="ErrTime"></a>

```go
var (
    // ErrTime indicates that the value is not a valid based on the given time format.
    ErrTime = NewCheckError("NOT_TIME")
)
```

<a name="Check"></a>
## func [Check](<https://github.com/cinar/checker/blob/main/checker.go#L32>)

```go
func Check[T any](value T, checks ...CheckFunc[T]) (T, error)
```

Check applies the given check functions to a value sequentially. It returns the final value and the first encountered error, if any.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	name := "    Onur Cinar    "

	name, err := v2.Check(name, v2.TrimSpace, v2.Required)
	if err != nil {
		fmt.Println(err)
		return
	}

	fmt.Println(name)
}
```

#### Output

```
Onur Cinar
```

</p>
</details>

<a name="CheckStruct"></a>
## func [CheckStruct](<https://github.com/cinar/checker/blob/main/checker.go#L62>)

```go
func CheckStruct(st any) (map[string]error, bool)
```

CheckStruct checks the given struct based on the validation rules specified in the "checker" tag of each struct field. It returns a map of field names to their corresponding errors, and a boolean indicating if all checks passed.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	type Person struct {
		Name string `checkers:"trim required"`
	}

	person := &Person{
		Name: "    Onur Cinar    ",
	}

	errs, ok := v2.CheckStruct(person)
	if !ok {
		fmt.Println(errs)
		return
	}

	fmt.Println(person.Name)
}
```

#### Output

```
Onur Cinar
```

</p>
</details>

<a name="CheckWithConfig"></a>
## func [CheckWithConfig](<https://github.com/cinar/checker/blob/main/checker.go#L47>)

```go
func CheckWithConfig[T any](value T, config string) (T, error)
```

CheckWithConfig applies the check functions specified by the config string to the given value. It returns the modified value and the first encountered error, if any.

<a name="HTMLEscape"></a>
## func [HTMLEscape](<https://github.com/cinar/checker/blob/main/html_escape.go#L19>)

```go
func HTMLEscape(value string) (string, error)
```

HTMLEscape applies HTML escaping to special characters.

<a name="HTMLUnescape"></a>
## func [HTMLUnescape](<https://github.com/cinar/checker/blob/main/html_unescape.go#L17>)

```go
func HTMLUnescape(value string) (string, error)
```

HTMLUnescape applies HTML unescaping to special characters.

<a name="IsASCII"></a>
## func [IsASCII](<https://github.com/cinar/checker/blob/main/ascii.go#L24>)

```go
func IsASCII(value string) (string, error)
```

IsASCII checks if the given string consists of only ASCII characters.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsASCII("Checker")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsAlphanumeric"></a>
## func [IsAlphanumeric](<https://github.com/cinar/checker/blob/main/alphanumeric.go#L24>)

```go
func IsAlphanumeric(value string) (string, error)
```

IsAlphanumeric checks if the given string consists of only alphanumeric characters.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsAlphanumeric("ABcd1234")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsAmexCreditCard"></a>
## func [IsAmexCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L80>)

```go
func IsAmexCreditCard(number string) (string, error)
```

IsAmexCreditCard checks if the given valie is a valid AMEX credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsAmexCreditCard("378282246310005")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsAnyCreditCard"></a>
## func [IsAnyCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L75>)

```go
func IsAnyCreditCard(number string) (string, error)
```

IsAnyCreditCard checks if the given value is a valid credit card number.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsAnyCreditCard("6011111111111117")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsCIDR"></a>
## func [IsCIDR](<https://github.com/cinar/checker/blob/main/cidr.go#L24>)

```go
func IsCIDR(value string) (string, error)
```

IsCIDR checks if the value is a valid CIDR notation IP address and prefix length.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsCIDR("2001:db8::/32")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsDigits"></a>
## func [IsDigits](<https://github.com/cinar/checker/blob/main/digits.go#L24>)

```go
func IsDigits(value string) (string, error)
```

IsDigits checks if the value contains only digit characters.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsDigits("123456")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsDinersCreditCard"></a>
## func [IsDinersCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L85>)

```go
func IsDinersCreditCard(number string) (string, error)
```

IsDinersCreditCard checks if the given valie is a valid Diners credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsDinersCreditCard("36227206271667")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsDiscoverCreditCard"></a>
## func [IsDiscoverCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L90>)

```go
func IsDiscoverCreditCard(number string) (string, error)
```

IsDiscoverCreditCard checks if the given valie is a valid Discover credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsDiscoverCreditCard("6011111111111117")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsEmail"></a>
## func [IsEmail](<https://github.com/cinar/checker/blob/main/email.go#L24>)

```go
func IsEmail(value string) (string, error)
```

IsEmail checks if the value is a valid email address.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsEmail("test@example.com")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsFQDN"></a>
## func [IsFQDN](<https://github.com/cinar/checker/blob/main/fqdn.go#L27>)

```go
func IsFQDN(value string) (string, error)
```

IsFQDN checks if the value is a valid fully qualified domain name \(FQDN\).

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsFQDN("example.com")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsGte"></a>
## func [IsGte](<https://github.com/cinar/checker/blob/main/gte.go#L25>)

```go
func IsGte[T cmp.Ordered](value, n T) (T, error)
```

IsGte checks if the value is greater than or equal to the given value.

<a name="IsHex"></a>
## func [IsHex](<https://github.com/cinar/checker/blob/main/hex.go#L23>)

```go
func IsHex(value string) (string, error)
```

IsHex checks if the given string consists of only hex characters.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsHex("0123456789abcdefABCDEF")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsIP"></a>
## func [IsIP](<https://github.com/cinar/checker/blob/main/ip.go#L24>)

```go
func IsIP(value string) (string, error)
```

IsIP checks if the value is a valid IP address.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsIP("192.168.1.1")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsIPv4"></a>
## func [IsIPv4](<https://github.com/cinar/checker/blob/main/ipv4.go#L24>)

```go
func IsIPv4(value string) (string, error)
```

IsIPv4 checks if the value is a valid IPv4 address.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsIPv4("192.168.1.1")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsIPv6"></a>
## func [IsIPv6](<https://github.com/cinar/checker/blob/main/ipv6.go#L24>)

```go
func IsIPv6(value string) (string, error)
```

IsIPv6 checks if the value is a valid IPv6 address.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsIPv6("2001:db8::1")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsISBN"></a>
## func [IsISBN](<https://github.com/cinar/checker/blob/main/isbn.go#L27>)

```go
func IsISBN(value string) (string, error)
```

IsISBN checks if the value is a valid ISBN\-10 or ISBN\-13.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsISBN("1430248270")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsJcbCreditCard"></a>
## func [IsJcbCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L95>)

```go
func IsJcbCreditCard(number string) (string, error)
```

IsJcbCreditCard checks if the given valie is a valid JCB 15 credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsJcbCreditCard("3530111333300000")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsLUHN"></a>
## func [IsLUHN](<https://github.com/cinar/checker/blob/main/luhn.go#L24>)

```go
func IsLUHN(value string) (string, error)
```

IsLUHN checks if the value is a valid LUHN number.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsLUHN("4012888888881881")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsLte"></a>
## func [IsLte](<https://github.com/cinar/checker/blob/main/lte.go#L25>)

```go
func IsLte[T cmp.Ordered](value, n T) (T, error)
```

IsLte checks if the value is less than or equal to the given value.

<a name="IsMAC"></a>
## func [IsMAC](<https://github.com/cinar/checker/blob/main/mac.go#L24>)

```go
func IsMAC(value string) (string, error)
```

IsMAC checks if the value is a valid MAC address.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsMAC("00:1A:2B:3C:4D:5E")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsMasterCardCreditCard"></a>
## func [IsMasterCardCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L100>)

```go
func IsMasterCardCreditCard(number string) (string, error)
```

IsMasterCardCreditCard checks if the given valie is a valid MasterCard credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsMasterCardCreditCard("5555555555554444")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsRegexp"></a>
## func [IsRegexp](<https://github.com/cinar/checker/blob/main/regexp.go#L20>)

```go
func IsRegexp(expression, value string) (string, error)
```

IsRegexp checks if the given string matches the given regexp expression.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsRegexp("^[0-9a-fA-F]+$", "ABcd1234")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsTime"></a>
## func [IsTime](<https://github.com/cinar/checker/blob/main/time.go#L47>)

```go
func IsTime(params, value string) (string, error)
```

IsTime checks if the given value is a valid time based on the given layout.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	value := "2024-12-31"

	_, err := v2.IsTime("DateOnly", value)
	if err != nil {
		panic(err)
	}
}
```

</p>
</details>

<details><summary>Example (Custom)</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	rfc3339Layout := "2006-01-02T15:04:05Z07:00"

	value := "2024-12-31T10:20:00Z07:00"

	_, err := v2.IsTime(rfc3339Layout, value)
	if err != nil {
		panic(err)
	}
}
```

</p>
</details>

<a name="IsURL"></a>
## func [IsURL](<https://github.com/cinar/checker/blob/main/url.go#L24>)

```go
func IsURL(value string) (string, error)
```

IsURL checks if the value is a valid URL.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsURL("https://example.com")
	if err != nil {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="IsUnionPayCreditCard"></a>
## func [IsUnionPayCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L105>)

```go
func IsUnionPayCreditCard(number string) (string, error)
```

IsUnionPayCreditCard checks if the given valie is a valid UnionPay credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsUnionPayCreditCard("6200000000000005")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="IsVisaCreditCard"></a>
## func [IsVisaCreditCard](<https://github.com/cinar/checker/blob/main/credit_card.go#L110>)

```go
func IsVisaCreditCard(number string) (string, error)
```

IsVisaCreditCard checks if the given valie is a valid Visa credit card.

<details><summary>Example</summary>
<p>


```go
package main

import (
	v2 "github.com/cinar/checker/v2"
)

func main() {
	_, err := v2.IsVisaCreditCard("4111111111111111")

	if err != nil {
		// Send the errors back to the user
	}
}
```

</p>
</details>

<a name="Lower"></a>
## func [Lower](<https://github.com/cinar/checker/blob/main/lower.go#L19>)

```go
func Lower(value string) (string, error)
```

Lower maps all Unicode letters in the given value to their lower case.

<a name="ReflectCheckWithConfig"></a>
## func [ReflectCheckWithConfig](<https://github.com/cinar/checker/blob/main/checker.go#L55>)

```go
func ReflectCheckWithConfig(value reflect.Value, config string) (reflect.Value, error)
```

ReflectCheckWithConfig applies the check functions specified by the config string to the given reflect.Value. It returns the modified reflect.Value and the first encountered error, if any.

<a name="RegisterLocale"></a>
## func [RegisterLocale](<https://github.com/cinar/checker/blob/main/check_error.go#L80>)

```go
func RegisterLocale(locale string, messages map[string]string)
```

RegisterLocale registers the localized error messages for the given locale.

<a name="RegisterMaker"></a>
## func [RegisterMaker](<https://github.com/cinar/checker/blob/main/maker.go#L54>)

```go
func RegisterMaker(name string, maker MakeCheckFunc)
```

RegisterMaker registers a new maker function with the given name.

<details><summary>Example</summary>
<p>


```go
package main

import (
	"fmt"
	"reflect"

	"github.com/cinar/checker/v2/locales"

	v2 "github.com/cinar/checker/v2"
)

func main() {
	locales.EnUSMessages["NOT_FRUIT"] = "Not a fruit name."

	v2.RegisterMaker("is-fruit", func(params string) v2.CheckFunc[reflect.Value] {
		return func(value reflect.Value) (reflect.Value, error) {
			stringValue := value.Interface().(string)

			if stringValue == "apple" || stringValue == "banana" {
				return value, nil
			}

			return value, v2.NewCheckError("NOT_FRUIT")
		}
	})

	type Item struct {
		Name string `checkers:"is-fruit"`
	}

	person := &Item{
		Name: "banana",
	}

	err, ok := v2.CheckStruct(person)
	if !ok {
		fmt.Println(err)
	}
}
```

</p>
</details>

<a name="Required"></a>
## func [Required](<https://github.com/cinar/checker/blob/main/required.go#L22>)

```go
func Required[T any](value T) (T, error)
```

Required checks if the given value of type T is its zero value. It returns an error if the value is zero.

<a name="Title"></a>
## func [Title](<https://github.com/cinar/checker/blob/main/title.go#L20>)

```go
func Title(value string) (string, error)
```

Title returns the value of the string with the first letter of each word in upper case.

<a name="TrimLeft"></a>
## func [TrimLeft](<https://github.com/cinar/checker/blob/main/trim_left.go#L19>)

```go
func TrimLeft(value string) (string, error)
```

TrimLeft returns the value of the string with whitespace removed from the beginning.

<a name="TrimRight"></a>
## func [TrimRight](<https://github.com/cinar/checker/blob/main/trim_right.go#L19>)

```go
func TrimRight(value string) (string, error)
```

TrimRight returns the value of the string with whitespace removed from the end.

<a name="TrimSpace"></a>
## func [TrimSpace](<https://github.com/cinar/checker/blob/main/trim_space.go#L19>)

```go
func TrimSpace(value string) (string, error)
```

TrimSpace returns the value of the string with whitespace removed from both ends.

<a name="URLEscape"></a>
## func [URLEscape](<https://github.com/cinar/checker/blob/main/url_escape.go#L17>)

```go
func URLEscape(value string) (string, error)
```

URLEscape applies URL escaping to special characters.

<a name="URLUnescape"></a>
## func [URLUnescape](<https://github.com/cinar/checker/blob/main/url_unescape.go#L17>)

```go
func URLUnescape(value string) (string, error)
```

URLUnescape applies URL unescaping to special characters.

<a name="Upper"></a>
## func [Upper](<https://github.com/cinar/checker/blob/main/upper.go#L19>)

```go
func Upper(value string) (string, error)
```

Upper maps all Unicode letters in the given value to their upper case.

<a name="CheckError"></a>
## type [CheckError](<https://github.com/cinar/checker/blob/main/check_error.go#L16-L22>)

CheckError defines the check error.

```go
type CheckError struct {
    // Code is the error code.
    Code string

    // data is the error data.
    Data map[string]interface{}
}
```

<a name="NewCheckError"></a>
### func [NewCheckError](<https://github.com/cinar/checker/blob/main/check_error.go#L35>)

```go
func NewCheckError(code string) *CheckError
```

NewCheckError creates a new check error with the given code.

<a name="NewCheckErrorWithData"></a>
### func [NewCheckErrorWithData](<https://github.com/cinar/checker/blob/main/check_error.go#L43>)

```go
func NewCheckErrorWithData(code string, data map[string]interface{}) *CheckError
```

NewCheckErrorWithData creates a new check error with the given code and data.

<a name="CheckError.Error"></a>
### func \(\*CheckError\) [Error](<https://github.com/cinar/checker/blob/main/check_error.go#L51>)

```go
func (c *CheckError) Error() string
```

Error returns the error message for the check.

<a name="CheckError.ErrorWithLocale"></a>
### func \(\*CheckError\) [ErrorWithLocale](<https://github.com/cinar/checker/blob/main/check_error.go#L65>)

```go
func (c *CheckError) ErrorWithLocale(locale string) string
```

ErrorWithLocale returns the localized error message for the check with the given locale.

<a name="CheckError.Is"></a>
### func \(\*CheckError\) [Is](<https://github.com/cinar/checker/blob/main/check_error.go#L56>)

```go
func (c *CheckError) Is(target error) bool
```

Is reports whether the check error is the same as the target error.

<a name="CheckFunc"></a>
## type [CheckFunc](<https://github.com/cinar/checker/blob/main/check_func.go#L11>)

CheckFunc is a function that takes a value of type T and performs a check on it. It returns the resulting value and any error that occurred during the check.

```go
type CheckFunc[T any] func(value T) (T, error)
```

<a name="MakeRegexpChecker"></a>
### func [MakeRegexpChecker](<https://github.com/cinar/checker/blob/main/regexp.go#L29>)

```go
func MakeRegexpChecker(expression string, invalidError error) CheckFunc[reflect.Value]
```

MakeRegexpChecker makes a regexp checker for the given regexp expression with the given invalid result.

<a name="MaxLen"></a>
### func [MaxLen](<https://github.com/cinar/checker/blob/main/max_len.go#L25>)

```go
func MaxLen[T any](n int) CheckFunc[T]
```

MaxLen checks if the length of the given value \(string, slice, or map\) is at most n. Returns an error if the length is greater than n.

<a name="MinLen"></a>
### func [MinLen](<https://github.com/cinar/checker/blob/main/min_len.go#L25>)

```go
func MinLen[T any](n int) CheckFunc[T]
```

MinLen checks if the length of the given value \(string, slice, or map\) is at least n. Returns an error if the length is less than n.

<a name="MakeCheckFunc"></a>
## type [MakeCheckFunc](<https://github.com/cinar/checker/blob/main/maker.go#L15>)

MakeCheckFunc is a function that returns a check function using the given params.

```go
type MakeCheckFunc func(params string) CheckFunc[reflect.Value]
```

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