Go RESTful Series

entities.go

package users

// ValidateUserUnique validates whether user's username or email is valid and returns errors or nil.
func ValidateUserUnique(userRepo UserRepository, user *User) error {
	errs := make([]error, 0)

	var exists bool
	var err error

	// Validate username.
	exists, err = userRepo.ExistsByUsername(user.Username)
	if err != nil {
		return err
	}
	if exists {
		errs = append(errs, ErrUsernameWasUsed)
	}

	// Validate email.
	exists, err = userRepo.ExistsByEmail(user.Email)
	if err != nil {
		return err
	}
	if exists {
		errs = append(errs, ErrEmailWasUsed)
	}

	// Return errors or nil.
	if len(errs) == 0 {
		return nil
	}
	return common.Errors(errs)
}