go-playground/validator · error

tag '%s' không thể dùng trên kiểu struct

Error message

tag '%s' không thể dùng trên kiểu struct

What it means

Raised inside the Vietnamese 'lt' translation registration when the field being translated is a struct. lt only applies to numeric kinds, strings, slices/maps/arrays (length) and time.Time; a generic struct has no 'less than' meaning, so the translator stops with this error. It fires when a struct field other than time.Time carries the lt tag.

Source

Thrown at translations/vi/vi.go:416

				case reflect.Slice, reflect.Map, reflect.Array:
					var c string

					err = fn()
					if err != nil {
						goto END
					}

					c, err = ut.C("lt-items-item", f64, digits, ut.FmtNumber(f64, digits))
					if err != nil {
						goto END
					}

					t, err = ut.T("lt-items", fe.Field(), c)

				case reflect.Struct:
					if fe.Type() != reflect.TypeOf(time.Time{}) {
						err = fmt.Errorf("tag '%s' không thể dùng trên kiểu struct", fe.Tag())
						goto END
					}

					t, err = ut.T("lt-datetime", fe.Field())

				default:
					err = fn()
					if err != nil {
						goto END
					}

					t, err = ut.T("lt-number", fe.Field(), ut.FmtNumber(f64, digits))
				}

			END:
				if err != nil {
					fmt.Printf("cảnh báo: lỗi chuyển ngữ FieldError: %s", err)
					return fe.(error).Error()

View on GitHub (pinned to facf128d2e)

Solutions

1. Remove the lt tag from the struct field
2. Apply lt to comparable inner fields instead
3. Use RegisterStructValidation for custom struct-wide rules
4. Verify datetime fields are exactly of type time.Time

When it happens

Trigger: Thrown at translations/vi/vi.go:416 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of go-playground/validator@facf128d2e (2026-09-02). Data as JSON: /api/errors/fac3656cb72cada0. Report an issue: GitHub.