main.go

Documentation: github.com/go-playground/validator/v10/_examples/custom

     1  package main
     2  
     3  import (
     4  	"database/sql"
     5  	"database/sql/driver"
     6  	"fmt"
     7  	"reflect"
     8  
     9  	"github.com/go-playground/validator/v10"
    10  )
    11  
    12  // DbBackedUser User struct
    13  type DbBackedUser struct {
    14  	Name sql.NullString `validate:"required"`
    15  	Age  sql.NullInt64  `validate:"required"`
    16  }
    17  
    18  // use a single instance of Validate, it caches struct info
    19  var validate *validator.Validate
    20  
    21  func main() {
    22  
    23  	validate = validator.New()
    24  
    25  	// register all sql.Null* types to use the ValidateValuer CustomTypeFunc
    26  	validate.RegisterCustomTypeFunc(ValidateValuer, sql.NullString{}, sql.NullInt64{}, sql.NullBool{}, sql.NullFloat64{})
    27  
    28  	// build object for validation
    29  	x := DbBackedUser{Name: sql.NullString{String: "", Valid: true}, Age: sql.NullInt64{Int64: 0, Valid: false}}
    30  
    31  	err := validate.Struct(x)
    32  
    33  	if err != nil {
    34  		fmt.Printf("Err(s):\n%+v\n", err)
    35  	}
    36  }
    37  
    38  // ValidateValuer implements validator.CustomTypeFunc
    39  func ValidateValuer(field reflect.Value) interface{} {
    40  
    41  	if valuer, ok := field.Interface().(driver.Valuer); ok {
    42  
    43  		val, err := valuer.Value()
    44  		if err == nil {
    45  			return val
    46  		}
    47  		// handle the error how you want
    48  	}
    49  
    50  	return nil
    51  }
    52
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