vendor/gopkg.in/go-playground/validator.v8/examples/struct-level/struct_level.go

   1 package main
   2
   3 import (
   4         "fmt"
   5         "reflect"
   6
   7         "gopkg.in/go-playground/validator.v8"
   8 )
   9
  10 // User contains user information
  11 type User struct {
  12         FirstName      string     `json:"fname"`
  13         LastName       string     `json:"lname"`
  14         Age            uint8      `validate:"gte=0,lte=130"`
  15         Email          string     `validate:"required,email"`
  16         FavouriteColor string     `validate:"hexcolor|rgb|rgba"`
  17         Addresses      []*Address `validate:"required,dive,required"` // a person can have a home and cottage...
  18 }
  19
  20 // Address houses a users address information
  21 type Address struct {
  22         Street string `validate:"required"`
  23         City   string `validate:"required"`
  24         Planet string `validate:"required"`
  25         Phone  string `validate:"required"`
  26 }
  27
  28 var validate *validator.Validate
  29
  30 func main() {
  31
  32         config := &validator.Config{TagName: "validate"}
  33
  34         validate = validator.New(config)
  35         validate.RegisterStructValidation(UserStructLevelValidation, User{})
  36
  37         validateStruct()
  38 }
  39
  40 // UserStructLevelValidation contains custom struct level validations that don't always
  41 // make sense at the field validation level. For Example this function validates that either
  42 // FirstName or LastName exist; could have done that with a custom field validation but then
  43 // would have had to add it to both fields duplicating the logic + overhead, this way it's
  44 // only validated once.
  45 //
  46 // NOTE: you may ask why wouldn't I just do this outside of validator, because doing this way
  47 // hooks right into validator and you can combine with validation tags and still have a
  48 // common error output format.
  49 func UserStructLevelValidation(v *validator.Validate, structLevel *validator.StructLevel) {
  50
  51         user := structLevel.CurrentStruct.Interface().(User)
  52
  53         if len(user.FirstName) == 0 && len(user.LastName) == 0 {
  54                 structLevel.ReportError(reflect.ValueOf(user.FirstName), "FirstName", "fname", "fnameorlname")
  55                 structLevel.ReportError(reflect.ValueOf(user.LastName), "LastName", "lname", "fnameorlname")
  56         }
  57
  58         // plus can to more, even with different tag than "fnameorlname"
  59 }
  60
  61 func validateStruct() {
  62
  63         address := &Address{
  64                 Street: "Eavesdown Docks",
  65                 Planet: "Persphone",
  66                 Phone:  "none",
  67                 City:   "Unknown",
  68         }
  69
  70         user := &User{
  71                 FirstName:      "",
  72                 LastName:       "",
  73                 Age:            45,
  74                 Email:          "Badger.Smith@gmail.com",
  75                 FavouriteColor: "#000",
  76                 Addresses:      []*Address{address},
  77         }
  78
  79         // returns nil or ValidationErrors ( map[string]*FieldError )
  80         errs := validate.Struct(user)
  81
  82         if errs != nil {
  83
  84                 fmt.Println(errs) // output: Key: 'User.LastName' Error:Field validation for 'LastName' failed on the 'fnameorlname' tag
  85                 //                               Key: 'User.FirstName' Error:Field validation for 'FirstName' failed on the 'fnameorlname' tag
  86                 err := errs.(validator.ValidationErrors)["User.FirstName"]
  87                 fmt.Println(err.Field) // output: FirstName
  88                 fmt.Println(err.Tag)   // output: fnameorlname
  89                 fmt.Println(err.Kind)  // output: string
  90                 fmt.Println(err.Type)  // output: string
  91                 fmt.Println(err.Param) // output:
  92                 fmt.Println(err.Value) // output:
  93
  94                 // from here you can create your own error messages in whatever language you wish
  95                 return
  96         }
  97
  98         // save user to database
  99 }