Muutoksiin reagoiminen Apex-käynnistimillä

Alla on esimerkki yksinkertaisesta säännöstä, joka lähettää ilmoituksen, kun tuote on loppumassa varastosta.

trigger LowOnStock on Products__ChangeEvent (after insert) {
    // Get the change event’s product ID for added and updated products
    Set<Id> productIds = new Set<Id>();
    for (Products__ChangeEvent event: Trigger.new) {
        if (event.ChangeEventHeader.getChangeType() != 'DELETE') {
            String productId = event.ChangeEventHeader.getRecordIds()[0];
            productIds.add(productId);
        }
    }
    if (productIds.size() > 0) {
        ProductNotifications.notifyOnLowOnStockProductUpdates(productIds);
    }
}

ProductNotifications-luokka kyselee ulkoisia Product-objekteja saadakseen muutetut tuotetunnukset ja LowOnStock-kynnysarvon. Nykyisten Product-tietueiden noutaminen ulkoisesta järjestelmä hyväksytyille tuotteille on callout, joka on ajoitettu Apex-futuurina.

public class ProductNotifications {    
    // Notify subscribers on product updates that are low on stock.
    // This method is run asynchronously as it is performing a callout to the external
    // system to get the latest product details
    @future (callout=true)
    public static void notifyOnLowOnStockProductUpdates(Set<Id> productIds) {
        // Look up the current stock threshold to filter the products with
        Integer productStockThreshold = ...;
        List<Products__x> lowOnStockProducts =
            getProductsLowOnStock(productIds, productStockThreshold);
        // Notify subscribers
        notifySubscribers(lowOnStockProducts,
            ‘These items are running out of stock. Act soon!’);
    }
    
    // Get the external Product objects for each Product ID
    public static List<Products__x>
    getProductsLowOnStock(Set<Id> productIds, Integer productStockThreshold) {
        return [SELECT Id, ExternalId, Name__c, ProductId__c, Stock__c, UnitPrice__c  
            FROM Products__x
            WHERE Stock__c < :productStockThreshold  AND Stock__c > 0 AND 
                Id IN :productIds];
    }
    
    // Notify subscribers by sending an email or SMS
    public static void notifySubscribers(String message, List<Products__x> products) {
        ...
    }
}