Prompt Share - REST Service to Update Product Quantity On Hand

[craigathon]

The Prompt Asked in Einstein Sidebar
Define an Apex REST class to handle inventory updates from an external system
It should accept a list of object with the following fields
ExternalId
QuantityOnHand

The ExternalId should match on existing Product2 records External_Id__c and update Quantity_On_Hand__c.
If there is no match for a given External Id, this should be logged to a custom Error Log object's Message field

The Result

@RestResource(urlMapping='/inventoryUpdate/*')
global with sharing class InventoryUpdateRestService {
    
    @HttpPost
    global static List<String> doInventoryUpdate(List<InventoryUpdate> inventoryUpdates) {
        List<String> successExternalIds = new List<String>();
        List<Error_Log__c> errorLogs = new List<Error_Log__c>();

        Map<String, Product2> externalIdToProductMap = new Map<String, Product2>();
        List<Product2> productsToUpdate = new List<Product2>();
        
        if(inventoryUpdates != null) {
            for(InventoryUpdate inventoryUpdate : inventoryUpdates) {
                if(inventoryUpdate.externalId != null && inventoryUpdate.quantityOnHand != null) {
                    externalIdToProductMap.put(inventoryUpdate.externalId, null);
                }
            }

            externalIdToProductMap.putAll([SELECT Id, Quantity_On_Hand__c, External_Id__c FROM Product2 WHERE External_Id__c IN :externalIdToProductMap.keySet() WITH USER_MODE]);

            for(InventoryUpdate inventoryUpdate : inventoryUpdates) {
                if(inventoryUpdate.externalId != null && inventoryUpdate.quantityOnHand != null) {
                    Product2 product = externalIdToProductMap.get(inventoryUpdate.externalId);

                    if(product != null) {
                        product.Quantity_On_Hand__c = inventoryUpdate.quantityOnHand;
                        productsToUpdate.add(product);
                    } else {
                        errorLogs.add(createErrorLog('No match found for External Id: ' + inventoryUpdate.externalId));
                    }
                }
            }

            if(productsToUpdate.size() > 0) {
                if(Product2.sObjectType.getDescribe().isUpdateable()) {
                    Database.update(productsToUpdate, true, AccessLevel.USER_MODE);
                }
            }

            if(errorLogs.size() > 0) {
                if(Error_Log__c.sObjectType.getDescribe().isCreateable()) {
                    Database.insert(errorLogs, true, AccessLevel.USER_MODE);
                }
            }
            
            for(Product2 product : productsToUpdate) {
                successExternalIds.add(product.External_Id__c);
            }
        }
        
        return successExternalIds;
    }

    global class InventoryUpdate {
        public String externalId;
        public Integer quantityOnHand;
    }

    private static Error_Log__c createErrorLog(String message) {
        Error_Log__c errorLog = new Error_Log__c();
        errorLog.Message__c = message;

        return errorLog;
    }
}

Thoughts

• The instructions were followed very well, logic works overall with just 1 significant miss
• Logging solution works correctly as prompted
• The issue was how the externalIdToProductMap was populated. The key needed to be the Product's External_Id__c and not Id. The externalIdToProductMap.putAll line could be updated such as:

for (Product2 p : [SELECT Id, Quantity_On_Hand__c, External_Id__c FROM Product2 
    WHERE External_Id__c IN :externalIdToProductMap.keySet() WITH USER_MODE]) {
    externalIdToProductMap.put(p.External_ID__c, p);
}