github.com/bytedance/go-tagexpr/v2@v2.9.8/validator/README.md

# validator [![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg?style=flat-square)](http://godoc.org/github.com/bytedance/go-tagexpr/v2/validator)

A powerful validator that supports struct tag expression.

## Feature

- Support for a variety of common operator
- Support for accessing arrays, slices, members of the dictionary
- Support access to any field in the current structure
- Support access to nested fields, non-exported fields, etc.
- Support registers validator function expression
- Built-in len, sprintf, regexp, email, phone functions
- Support simple mode, or specify error message mode
- Use offset pointers to directly take values, better performance
- Required go version ≥1.9

## Example

```go
package validator_test

import (
	"fmt"

	vd "github.com/bytedance/go-tagexpr/v2/validator"
)

func Example() {
	type InfoRequest struct {
		Name         string   `vd:"($!='Alice'||(Age)$==18) && regexp('\\w')"`
		Age          int      `vd:"$>0"`
		Email        string   `vd:"email($)"`
		Phone1       string   `vd:"phone($)"`
		OtherPhones  []string `vd:"range($, phone(#v,'CN'))"`
		*InfoRequest `vd:"?"`
		Info1        *InfoRequest `vd:"?"`
		Info2        *InfoRequest `vd:"-"`
	}
	info := &InfoRequest{
		Name:        "Alice",
		Age:         18,
		Email:       "henrylee2cn@gmail.com",
		Phone1:      "+8618812345678",
		OtherPhones: []string{"18812345679", "18812345680"},
	}
	fmt.Println(vd.Validate(info))

	type A struct {
		A    int `vd:"$<0||$>=100"`
		Info interface{}
	}
	info.Email = "xxx"
	a := &A{A: 107, Info: info}
	fmt.Println(vd.Validate(a))
	type B struct {
		B string `vd:"len($)>1 && regexp('^\\w*$')"`
	}
	b := &B{"abc"}
	fmt.Println(vd.Validate(b) == nil)

	type C struct {
		C bool `vd:"@:(S.A)$>0 && !$; msg:'C must be false when S.A>0'"`
		S *A
	}
	c := &C{C: true, S: a}
	fmt.Println(vd.Validate(c))

	type D struct {
		d []string `vd:"@:len($)>0 && $[0]=='D'; msg:sprintf('invalid d: %v',$)"`
	}
	d := &D{d: []string{"x", "y"}}
	fmt.Println(vd.Validate(d))

	type E struct {
		e map[string]int `vd:"len($)==$['len']"`
	}
	e := &E{map[string]int{"len": 2}}
	fmt.Println(vd.Validate(e))

	// Customizes the factory of validation error.
	vd.SetErrorFactory(func(failPath, msg string) error {
		return fmt.Errorf(`{"succ":false, "error":"validation failed: %s"}`, failPath)
	})

	type F struct {
		f struct {
			g int `vd:"$%3==0"`
		}
	}
	f := &F{}
	f.f.g = 10
	fmt.Println(vd.Validate(f))

	fmt.Println(vd.Validate(map[string]*F{"a": f}))
	fmt.Println(vd.Validate(map[string]map[string]*F{"a": {"b": f}}))
	fmt.Println(vd.Validate([]map[string]*F{{"a": f}}))
	fmt.Println(vd.Validate(struct {
		A []map[string]*F
	}{A: []map[string]*F{{"x": f}}}))
	fmt.Println(vd.Validate(map[*F]int{f: 1}))
	fmt.Println(vd.Validate([][1]*F{{f}}))
	fmt.Println(vd.Validate((*F)(nil)))
	fmt.Println(vd.Validate(map[string]*F{}))
	fmt.Println(vd.Validate(map[string]map[string]*F{}))
	fmt.Println(vd.Validate([]map[string]*F{}))
	fmt.Println(vd.Validate([]*F{}))

	// Output:
	// <nil>
	// email format is incorrect
	// true
	// C must be false when S.A>0
	// invalid d: [x y]
	// invalid parameter: e
	// {"succ":false, "error":"validation failed: f.g"}
	// {"succ":false, "error":"validation failed: {v for k=a}.f.g"}
	// {"succ":false, "error":"validation failed: {v for k=a}{v for k=b}.f.g"}
	// {"succ":false, "error":"validation failed: [0]{v for k=a}.f.g"}
	// {"succ":false, "error":"validation failed: A[0]{v for k=x}.f.g"}
	// {"succ":false, "error":"validation failed: {k}.f.g"}
	// {"succ":false, "error":"validation failed: [0][0].f.g"}
	// unsupport data: nil
	// <nil>
	// <nil>
	// <nil>
	// <nil>
}
```

## Syntax

Struct tag syntax spec:

```
type T struct {
	// Simple model
    Field1 T1 `tagName:"expression"`
	// Specify error message mode
    Field2 T2 `tagName:"@:expression; msg:expression2"`
	// Omit it
    Field3 T3 `tagName:"-"`
    // Omit it when it is nil
    Field4 T4 `tagName:"?"`
    ...
}
```

|Operator or Operand|Explain|
|-----|---------|
|`true` `false`|boolean|
|`0` `0.0`|float64 "0"|
|`''`|String|
|`\\'`| Escape `'` delims in string|
|`\"`| Escape `"` delims in string|
|`nil`|nil, undefined|
|`!`|not|
|`+`|Digital addition or string splicing|
|`-`|Digital subtraction or negative|
|`*`|Digital multiplication|
|`/`|Digital division|
|`%`|division remainder, as: `float64(int64(a)%int64(b))`|
|`==`|`eq`|
|`!=`|`ne`|
|`>`|`gt`|
|`>=`|`ge`|
|`<`|`lt`|
|`<=`|`le`|
|`&&`|Logic `and`|
|`\|\|`|Logic `or`|
|`()`|Expression group|
|`(X)$`|Struct field value named X|
|`(X.Y)$`|Struct field value named X.Y|
|`$`|Shorthand for `(X)$`, omit `(X)` to indicate current struct field value|
|`(X)$['A']`|Map value with key A or struct A sub-field in the struct field X|
|`(X)$[0]`|The 0th element or sub-field of the struct field X(type: map, slice, array, struct)|
|`len((X)$)`|Built-in function `len`, the length of struct field X|
|`mblen((X)$)`|the length of string field X (character number)|
|`regexp('^\\w*$', (X)$)`|Regular match the struct field X, return boolean|
|`regexp('^\\w*$')`|Regular match the current struct field, return boolean|
|`sprintf('X value: %v', (X)$)`|`fmt.Sprintf`, format the value of struct field X|
|`range(KvExpr, forEachExpr)`|Iterate over an array, slice, or dictionary <br> - `#k` is the element key var <br> - `#v` is the element value var <br> - `##` is the number of elements <br> - e.g. [example](../spec_range_test.go)|
|`in((X)$, enum_1, ...enum_n)`|Check if the first parameter is one of the enumerated parameters|
|`email((X)$)`|Regular match the struct field X, return true if it is email|
|`phone((X)$,<'defaultRegion'>)`|Regular match the struct field X, return true if it is phone|

<!-- |`(X)$k`|Traverse each element key of the struct field X(type: map, slice, array)|
|`(X)$v`|Traverse each element value of the struct field X(type: map, slice, array)| -->

<!-- |`&`|Integer bitwise `and`|
|`\|`|Integer bitwise `or`|
|`^`|Integer bitwise `not` or `xor`|
|`&^`|Integer bitwise `clean`|
|`<<`|Integer bitwise `shift left`|
|`>>`|Integer bitwise `shift right`| -->

Operator priority(high -> low):

* `()` `!` `bool` `float64` `string` `nil`
* `*` `/` `%`
* `+` `-`
* `<` `<=` `>` `>=`
* `==` `!=`
* `&&`
* `||`