Custom validators

It is also possible to register custom validators. See the example code.

  1. package main
  3. import (
  4.     "net/http"
  5.     "time"
  7.     "github.com/gin-gonic/gin"
  8.     "github.com/gin-gonic/gin/binding"
  9.     "github.com/go-playground/validator/v10"
  10. )
  12. // Booking contains binded and validated data.
  13. type Booking struct {
  14.     CheckIn  time.Time `form:"check_in" binding:"required,bookabledate" time_format:"2006-01-02"`
  15.     CheckOut time.Time `form:"check_out" binding:"required,gtfield=CheckIn,bookabledate" time_format:"2006-01-02"`
  16. }
  18. var bookableDate validator.Func = func(fl validator.FieldLevel) bool {
  19.     date, ok := fl.Field().Interface().(time.Time)
  20.     if ok {
  21.         today := time.Now()
  22.         if today.After(date) {
  23.             return false
  24.         }
  25.     }
  26.     return true
  27. }
  29. func main() {
  30.     route := gin.Default()
  32.     if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
  33.         v.RegisterValidation("bookabledate", bookableDate)
  34.     }
  36.     route.GET("/bookable", getBookable)
  37.     route.Run(":8085")
  38. }
  40. func getBookable(c *gin.Context) {
  41.     var b Booking
  42.     if err := c.ShouldBindWith(&b, binding.Query); err == nil {
  43.         c.JSON(http.StatusOK, gin.H{"message": "Booking dates are valid!"})
  44.     } else {
  45.         c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
  46.     }
  47. }
  1. $ curl "localhost:8085/bookable?check_in=2118-04-16&check_out=2118-04-17"
  2. {"message":"Booking dates are valid!"}
  4. $ curl "localhost:8085/bookable?check_in=2118-03-10&check_out=2118-03-09"
  5. {"error":"Key: 'Booking.CheckOut' Error:Field validation for 'CheckOut' failed on the 'gtfield' tag"}

Struct level validations can also be registered this way. See the struct-lvl-validation example to learn more.

Last modified August 1, 2020 : chore: update Custom validators (a39a8b4)