saveField for $this->request->data and multiple models

gistfile1.php

public function saveField() {

		$this->autoRender = false;

		if (!$this->request->data) {
			return json_encode(array(
				'failed' => true,
				'newValue' => '',
				'message' => 'Data missing',
			));
		}

		// User or Profile Model
		$model = key($this->request->data);

		// Profile ID or User ID
		$id = $this->request->data[$model]['id'];

		// Check that the logged in user is the owner of the profile
		// Skip if admin
		$role = $this->Auth->user('Role.alias');
		if ($role != "admin") {
			if (!$this->Auth->user("$model.id") == $id) {
				return json_encode(array(
					'failed' => true,
					'newValue' => '',
					'message' => 'Security error'
				));
			}
		}
		// Validate data and save with fieldList
		$this->{$model}->id = $Id;
		if (!$this->{$model}->save($this->request->data)) {
			return json_encode(array(
				'failed' => true,
				'newValue' => $value,
				'message' => "Saving $fieldName failed"
			));
		}

	 }