HABTM form validation in CakePHP

Question

I have a Projects table and a Users table which are linked by a HABTM relation. In the \"add\" new Project page I have a multiple checkbox section to select Users for the ne

Answer 1

Try this:

// app/models/project.php
/**
 * An additional validation check to ensure at least one User is
 * selected. Spoofs Cake into thinking that there are validation
 * errors on the Project model by invalidating a non-existent field
 * on the Project model, then also invalidates the habtm field as
 * well, so when the form is re-displayed, the error is displayed
 * on the User field.
 **/
function beforeValidate() {
  if (!isset($this->data['User']['User'])
  || empty($this->data['User']['User'])) {
    $this->invalidate('non_existent_field'); // fake validation error on Project
    $this->User->invalidate('User', 'Please select at least one user');
  }
  return true;
}