How to perform conditional required validation ussing ozzo validation in golang? - validation

Question

In Golang ozzo-validation, how can I validate a field which is dependent on another field ?
For example, if I have the following:
return validation.ValidateStruct(&c,
validation.Field(&c.Name, validation.Required, validation.Length(5, 20)),
validation.Field(&c.Gender, validation.In("Female", "Male")),
validation.Field(&c.Email, is.Email),
validation.Field(&c.Address),
How can I add a validation that the Address is required only if email is not empty?

Answer 1

You can achieve it in two ways-
Adding your own custom rules
Conditionally add FieldRules based on precondition-value i.e check Email while creating field rules then supply it to validation.ValidateStruct
For e.g.:
type Sample struct {
Name string
Gender string
Email string
Address Address
}
type Address struct {
// ... fields
}
func (s Sample) Validate() error {
var fieldRules []*validation.FieldRules
fieldRules = append(fieldRules, validation.Field(&s.Name, validation.Required, validation.Length(5, 20)))
fieldRules = append(fieldRules, validation.Field(&s.Gender, validation.In("Female", "Male")))
fieldRules = append(fieldRules, validation.Field(&s.Email, is.Email))
if len(strings.TrimSpace(s.Email)) > 0 {
fieldRules = append(fieldRules, validation.Field(&s.Address, validation.Required))
fieldRules = append(fieldRules, validation.Field(&s.Address))
}
return validation.ValidateStruct(&s, fieldRules...)
}

Answer 2

The library now supports conditional validation by the validation.When function.
Here is a code snipped which fits the validation you described.
package main
import (
"fmt"
validation "github.com/go-ozzo/ozzo-validation" // or "github.com/go-ozzo/ozzo-validation/v4" if "When" not found
)
type Entry struct {
Name string
Gender string
Email string
Address string
}
func main() {
v := func(e Entry) {
fmt.Println(validation.ValidateStruct(&e,
validation.Field(&e.Name, validation.Required, validation.Length(5, 20)),
// Note that if gender is "" and not required, validation returns no error.
validation.Field(&e.Gender, validation.Required, validation.In("Female", "Male")),
validation.Field(&e.Address, validation.When(e.Email != "", validation.Required.Error("Address is required if Email is set"))),
))
}
// All is fine for no Email.
e := Entry{
Name: "My name is!",
Gender: "Male",
}
v(e)
// Validation fails for Email and no Address.
e = Entry{
Name: "My name is!",
Gender: "Male",
Email: "a#org.com",
}
v(e)
}
It outputs.
<nil>
Address: Address is required if Email is set.
The library documentation describes it as well: https://github.com/go-ozzo/ozzo-validation#conditional-validation