Attachment ID, Logic - google-glass

Question

I have a Card, with this
try {
$menu_items = array();
$card = new \Google_Service_Mirror_TimelineItem();
//$card->setText("Test");
$card->setHtml('<img src="attachment:0"><img src="attachment:1">');
$menu_item = new \Google_Service_Mirror_MenuItem();
$menu_item->setAction("DELETE");
array_push($menu_items, $menu_item);
$card->setMenuItems($menu_items);
$opt_params = array();
$sr = $this->service->timeline->insert($card, $opt_params);
error_log('Send Card');
error_log(print_r($sr,true));
//return $sr;
$itemId = $sr->getId();
$params = array(
'data' => file_get_contents('https://XXXX.com/1.jpg'),
'mimeType'=>'image/jpg',
'uploadType' => 'media'
);
$sr = $this->service->timeline_attachments->insert($itemId, $params);
error_log('Send Card Attachment');
error_log(print_r($sr,true));
$params = array(
'data' => file_get_contents('https://XXXX.com/2.jpg'),
'mimeType'=>'image/jpg',
'uploadType' => 'media'
);
$sr = $this->service->timeline_attachments->insert($itemId, $params);
error_log('Send Card Attachment');
error_log(print_r($sr,true));
} catch (\Exception $e) {
error_log('Error while sending card '.$e->getMessage());
}
This works.
I get a card with two images.
Documentation states that I can use the attachments ids.. what is the logic behind that? for updates/patch only?
Aso, I am guessing if I send a card, and then I push the files, I would need to set notification.deliveryTime to the near future to avoid a weird card while the files are being uploaded?

Answer 1

It depends on the exact use. Some of the frameworks allow the attachments to be uploaded at the same time as the HTML for the card, so you'll be sure of the order and be sure that everything is available at once.
If you're uploading the attachments separately, it makes sense to use the attachment id that is returned when you do the upload since you have the information.
Good thought, but I wouldn't go with playing with notification.deliveryTime, since it hasn't worked very well the times I've tried using it. Instead, you might want to post the original card with some text such as "Loading..." and not send the notification at all. Then, when the attachments are uploaded, update the card to reference the attachments and set the notification so it generates the audio.
Update:
As you've noticed, you can't upload an attachment and attach it to multiple cards for the same reason you can't create a single timeline item and send it to multiple people - security. Attachments "belong" to a timeline item in the same way timeline items "belong" to a person. This is somewhat analogous to email and attachments - once you send the email out, each email has its own copy of the attachment.