Custom Validators

Valgo is designed to be extended. A custom validator typically wraps a *valgo.ValidatorContext and exposes rule methods that add checks.

The pattern used in custom/custom_validator_test.go looks like this:

var secretWordLocale = &valgo.Locale{
  "not_valid_secret": "{{title}} is invalid.",
}

type ValidatorSecretWord struct {
  context *valgo.ValidatorContext
}

func (v *ValidatorSecretWord) Correct(template ...string) *ValidatorSecretWord {
  v.context.Add(
    func() bool {
      s := v.context.Value().(string)
      return s == "cohesive" || s == "stack"
    },
    "not_valid_secret",
    template...,
  )
  return v
}

func (v *ValidatorSecretWord) Context() *valgo.ValidatorContext {
  return v.context
}

func SecretWord(value string, nameAndTitle ...string) *ValidatorSecretWord {
  context := valgo.NewContext(value, nameAndTitle...)
  context.WithLocaleFallback(secretWordLocale)

  return &ValidatorSecretWord{context: context}
}

WithLocaleFallback(...) lets a custom validator provide default messages for its own error keys. Fallback entries are used only when the active validation locale does not define the key, so consumers can still override not_valid_secret with Options{Locale: ...}.