无法在HABTM表中添加新记录

Question

I want to add a new record in a table called TutorsSubject. This table is created from HABTM relationship of Tutor and Subject. Anyway I load the subject names in a text box and I can select a subject name but I cant add a new record. I need to set the id of the tutor_id. There are 3 fields in the tutorsSubject table called id,tutor_id and subject_id. I only need to select in 1 field which is the subject_id from a list of names found in the subject table, and then set the tutor_id manually.

Currently I am able to select from a list of subject names but I cant add a new record with the subject name and set tutor_id.

Error: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails

class TutorsSubjectsController extends AppController {

public function tutoradd() {

 $this->loadModel('Subject');  

         $options['recursive']=-1; 
           $options['fields']=array('Subject.name');
          $te2= $this->Subject->find('list',$options);
     debug($te2);
    $this->set( 'te',$te2);




//put is for edit and post for new record
    if ($this->request->is('post')) {

          $this->request->data['TutorsSubject']['tutor_id']=2; 
        debug($this->request->data);
        if ($this->TutorsSubject->save($this->request->data)) {
            $this->Session->setFlash(__('Your post has been updated.'));
            return $this->redirect(array('controller' => 'tutors','action' => 'tutordetails'));
        }
        $this->Session->setFlash(__('Unable to update your post.'));
    }


   //View which works fine as it displays the list 
           echo $this->Form->create('TutorsSubject', array('type' => 'post'));


            echo $this->Form->input('tutorsSubject.subject_id', array('options' => $te));
             echo $this->Form->end('Save Post');

//model subject
public $hasAndBelongsToMany = array(

        'Tutor' => array(
            'className' => 'Tutor',
            'joinTable' => 'tutors_subjects',
            'foreignKey' => 'subject_id',
            'associationForeignKey' => 'tutor_id',
            'unique' => 'keepExisting',
            'conditions' => '',
            'fields' => '',
            'order' => '',
            'limit' => '',
            'offset' => '',
            'finderQuery' => '',
            'deleteQuery' => '',
            'insertQuery' => ''
        )
    );

//model tutor
  public $hasAndBelongsToMany = array(
        'Subject' => array(
            'className' => 'Subject',
            'joinTable' => 'tutors_subjects',
            'foreignKey' => 'tutor_id',
            'associationForeignKey' => 'subject_id',
            'unique' => 'keepExisting',
            'conditions' => '',
            'fields' => '',
            'order' => '',
            'limit' => '',
            'offset' => '',
            'finderQuery' => '',
            'deleteQuery' => '',
            'insertQuery' => ''
        ),

    );