CakePHP pre populate select box based on existing selection on related model

I am trying to pre-populate this State select box with the existing selection when editing records. in a related model.

plan_details/view.ctp

echo $this->Form->input('State',array('emp开发者_Python百科ty' => false,'options' => $state));

plan_details_controller view function:

$state = $this->PlanDetail->Plan->State->find('list');
    $this->set(compact('state', $state));
    debug($state);

Array output in view.ctp (as expected):

Array
(
    [1] => Oregon
    [2] => Washington
)

My select box above defaults to 1 in the array. I need it to default to the already existing selected value.

For example, when I added a record and a selected Washington(2), then when viewing my edit screen, the pre-selected value should be Washington with value 2.

I'm stuck and cracking at this for a while. Any idea what I am doing wrong?

If you are editing a page you need to set $this->data to auto populate it. Within your edit action

if (empty($this->data)) {
     $this->data = $this->PlanDetail->read(null, $id);
}

This should read in the record then ( note the plural )

$states = $this->PlanDetail->Plan->State->find('list');
$this->set(compact('states'));

In your form it should read

echo $this->Form->input('Plan.state_id',array('empty' => false));

I find your approach a bit confusing but the above should work. Is this form for editing a Plan, PlanDetail or both