Backend validation rules

The plugin comes with some inbuilt validation rules. Here is the list of the inbuilt rules:

Besides the built-in validation rules, the plugin also provides a possibility to register custom validation rules. Creating a custom validation rule is as easy as creating a child class of \XPACGroup\Plugin\XPACForms\Rules\Rule class. The parent class implements all required logic and requires 4 abstract methods to be implemented in the child class:

1. public static function getName: This method is designed to return the rule’s unique name. The return value should be a string.
2. protected function isActive: This method is designed to indicate whether the validation rule should validate the value. It receives an associative array representing the parsed block. The return value should be a boolean true – indicating that the rule should validate the value; a boolean false – vice versa.
3. public static function getMessage: This method is designed to return the validation message of the rule. It optionally receives its own instance during the validation. The return value should be a string representing the validation rule for the user.
4. protected function validate: This method is designed to implement the validation. It receives 2 arguments:

It should implement the validation logic and return a boolean true indicating that the value is valid, and a boolean false – otherwise.

Optionally, the constructor method of the rule class is available to be overwritten in the child class, which will receive 2 arguments.

Don’t forget to call the parent::__construct($block, $options); in the rule constructor during the overwriting.

<?php

class CustomRule extends Rule
{
    /**
     * Get a unique name.
     * @return string
     */
    final public static function getName(): string
    {
        return 'custom-rule';
    }

    /**
     * Check whether the rule is active.
     * @param   array  $block  Parsed block.
     * @return bool
     */
    protected function isActive(array $block): bool
    {
        if ('some_field_name' === $block['attrs']['name']) {
            return true;
        }
        return false;
    }

    /**
     * Get the error message.
     * @param   XPACGroup\Plugin\XPACForms\Rules\Rule|null  $rule  Optional: Rule instance.
     * @return string
     */
    public static function getMessage($rule = null)
    {
        $message = __('My awesome validation message', 'textdomain');
        return parent::prepareMessage($message, $rule);
    }

    /**
     * Validate provided value.
     * @param   mixed                                        $value       Value to validate.
     * @param   \XPACGroup\Plugin\XPACForms\Core\Submission  $submission     Submission instance.
     *
     * @return bool
     */
    public function validate($value, $submission): bool
    {
        return 10 === $value;
    }
}

The parent rule-class additionally implements the validation message modification functionality via a dynamic xpac_forms_validation_{$name}_rule_message filter, where the $name is the rule’s unique name and provides a possibility to overwrite default validation messages. The callback hooked in the mentioned dynamic filter will receive the 2 arguments and should return the updated validation message.

Example:

function edit_required_rule_message($message, $rule) {
	return "Hello World";
}
add_filter( 
     'xpac_forms_validation_required_rule_message', 
     'edit_required_rule_message', 
     10,
     2 
);