Can't create quickform via CRM_Core_Form in my custom extension

Question

I want to create page with form via my custom extension. I find this page in documentation: https://docs.civicrm.org/dev/en/latest/framework/quickform/ But when I create a class according to the documentation, I get this error:

Error: Call to a member function setName() on string in CRM_Core_Form->__construct() (line 271 of /var/www/mvp1/web/sites/all/modules/civicrm/CRM/Core/Form.php).

My class:

class CRM_JosiahVenture_Page_RolePrimaryAlert extends CRM_Core_Form {

  public function preProcess() {
  }

  public function buildQuickForm() {
    $this->add('text', 'my_text_field', ts('Enter Some Text'));
  }

  public function addRules() {
    $this->addFormRule(array('CRM_Example_Form', 'myRules'));
  }

  public static function myRules($values) {
    $errors = array();
    if ($values['foo'] != 'abc') {
      $errors['foo'] = ts('You entered the wrong text!');
    }
    return empty($errors) ? TRUE : $errors;
  }

  public function postProcess() {
  }
}

My xml file:

<item>
    <path>civicrm/RolePrimary</path>
    <page_callback>CRM_JosiahVenture_Page_RolePrimaryAlert</page_callback>
    <title>CustomActivity</title>
    <access_arguments>access CiviCRM</access_arguments>
  </item>

Tpl file is empty for now.

Answer 1

Maybe it is not connected to your issue, but if you implement a form, it supposed to be inside a Form directory, and the class name should follow this (has to contain _Form_). In your case the class name contains the _Page_ string which is strange. I would like to suggest you to generate the basics of your form with the civix tool. After the file generation you can check that the dummy form works well or not. If it works well, you can start to modify the dummy code.

Answer 2

In preprocess/postprocess/buildquickform, you should call the parent, i.e. your class should be:

class CRM_JosiahVenture_Page_RolePrimaryAlert extends CRM_Core_Form {

  public function preProcess() {
    parent::preProcess(); // <-- ************ add this
  }

  public function buildQuickForm() {
    parent::buildQuickForm();  // <-- ************ and this
    $this->add('text', 'my_text_field', ts('Enter Some Text'));
  }

  public function addRules() {
    $this->addFormRule(array('CRM_Example_Form', 'myRules'));
  }

  public static function myRules($values) {
    $errors = array();
    if ($values['foo'] != 'abc') {
      $errors['foo'] = ts('You entered the wrong text!');
    }
    return empty($errors) ? TRUE : $errors;
  }

  public function postProcess() {
    parent::postProcess();  // <-- ************ and this
  }
}