Thursday, 1 November 2018

Lazy Loading Menu Count

I've been using the lazy loading concept demonstrated in Maxime's post quite a lot recently, I'd love to see this as a declarative feature one day.

I also wondered if I could apply this concept to the badge count in the side menu - not slow the page load by a longer running query that populates the count.

Turns out it wasn't that hard, particularly since I already had the jQuery I needed from a previous requirement.

We first need to add a unique class to the link definition, so we can identify the menu item that needs updating.

The label contains the substitution string reference to an application item called LAZY_MENU, that is just computed to zero on each page load.
Surrounded by square brackets, this turns it into the count badge.

Add a dynamic action that executes PL/SQL on Page Load, probably to the global page, though this demo only fires when on page 15.

The demo populates the item based on a query that counts how many columns in my schema, plus a random number, so we can see it change each time.

A subsequent JavaScript action is where the real action is at
$('#t_TreeNav span.lazy-menu')
The selector identifies the menu item based on the lazy-menu class entered in the link definition, then traverses the tree to locate the relevant badge, which is then updated to the page item.

A more complete solution may also update LAZY_MENU application item, ready to have reasonably fresh information for the next page load.

Or we could make our queries faster ;p