Computed Values in the Feed

A value can be stored when an activity is published, updated when its model is saved, or computed when the feed is retrieved. Computing on retrieval keeps values current even when changes to other models affect them.

Storing a Value at Publication

Use ->data() to store facts about the moment an activity was published. For example, record the old and new prices when a menu item's price changes:

use Storyfeed\Facades\Storyfeed;

Storyfeed::activity()
    ->by($staff)
    ->action('reprice', $menuItem)
    ->data(['old_price' => $oldPrice, 'new_price' => $menuItem->price]) 
    ->publish();

The activity keeps those prices after later changes. Values in the model's toFeed() snapshot instead update when that model is saved.

Computing a Value When the Feed Is Retrieved

A menu item's order count changes when an order is placed, even if the menu item itself is not saved. Return a closure body from feedMedia() to compute the count when the feed is retrieved. Assuming the model defines an orders relationship, pass it to $context->model(withCount: ['orders']):

app/Models/MenuItem.php

use Storyfeed\Body\KeyValue;
use Storyfeed\FeedContext;
use Storyfeed\FeedMedia;

public static function feedMedia(FeedContext $context): ?FeedMedia
{
    return FeedMedia::make()
        ->body(
            function () use ($context): KeyValue {
                $menuItem = $context->model(withCount: ['orders']); 

                return KeyValue::make()
                    ->title($menuItem?->name)
                    ->items('Orders', $menuItem?->orders_count);
            },
        );
}

Models load once per model class for the page, with the requested counts loaded together. The closure defers building the body until the payload needs it. If a body resolver throws, Storyfeed reports the error and drops only that body; the activity and its other bodies remain.

The menu item uses a KeyValue body to display its current order count:

SH

Steve Harrington added a menu item, USS Butterscotch4d ago

USS Butterscotch

Price

$2.95

Section

Sundaes

Available

At the counter

Orders

12

Choosing Between Them

Compute a value on retrieval when a stale value would mislead someone using the page. For example, a page that lets people place orders should retrieve the current order count. The displayed value updates the next time the feed is retrieved.

Store a value in activity data when it describes history, such as the prices before and after a change. Use toFeed() for the model's own current facts, such as its name or description, which update with the model.