Populating a dropdown list in Cakephp from database values - database

Question

I'm trying to populate the values in a dropdown list in Cakephp v2.6.1.
The values are being retrieved, but the form helper is not creating dropdown listboxes as expected: All I am getting displayed on the form is the Submit button - The id fields are send as hidden fields to the web page. Can someone point out where I am going wrong?
Coursemembership controller
<?php
App::uses('AppController', 'Controller');
class CoursemembershipsController extends AppController {
public $components = array('Paginator', 'Session');
...
public function add() {
if ($this->request->is('post')) {
$this->Coursemembership->create();
if ($this->Coursemembership->save($this->request->data)) {
$this->Session->setFlash(__('The coursemembership has been saved.'));
if ($this->Coursemembership->saveAssociated($this->request->data)) {
return $this->redirect(array('action' => 'index'));
} else {
$this->Session->setFlash(__('The coursemembership could not be saved. Please, try again.'));
}
}
}
$students = $this->Coursemembership->Student->find('list');
$courses = $this->Coursemembership->Course->find('list');
$this->set(compact('students', 'courses'));
}
Add view
<div class="coursememberships form">
<?php echo $this->Form->create('Coursemembership'); ?>
<?php echo $this->Form->input('Student.id'); ?>
<?php echo $this->Form->input('Course.id'); ?>
<?php echo $this->Form->end(__('Submit')); ?>
</div>
Variables (from the debug add-in)
View Variables
students(array)
1Cromwell
2Lionheart
3Knight
7four
8five
9six
10seven
11eight
courses(array)
1Applied Speliology
2Aggravated aggrandisement
3Crossword Puzzles 101
5Aggravated aggrandisement
6Applied Speliology

Answer 1

You're not setting the field names for your inputs properly. The id field is the primary key by convention and will be added as a hidden field (usually used for editing, so your Model knows what id to alter).
You should add the fields as they are set in the Coursemembership datasource (probably a database table called coursememberships, if you're following convention for database design). This should show the fields you need and save the proper data:
echo $this->Form->create('Coursemembership');
echo $this->Form->input('Coursemembership.student_id');
echo $this->Form->input('Coursemembership.course_id');
echo $this->Form->end(__('Submit'));
Everything you want to save should go to the Coursemembership model. You should only need to save anything to the Student or Course model if you'd actually wanted to add a new student or course to your application. For assigning a membership of a Student to a Course, the above code should do the trick.