In the first part of this post I outlined the issues involved with creating a trigger to do roll-up summaries with a lookup relationship. To solve the problem I did what you should always try to do first: let the Force.com platform do the heavy lifting for you. Don't try to code around the platform when the declarative interface will do the trick 99% of the time. You'll be amazed with the things you can do with the platform when you let it. The rule of thumb is to use the point-n-click Builder first and write code only as a last resort.
So to solve my problem I added another custom object called Shipment Item and created a Master-Detail(Shipment) field that would automatically provide the roll-up summaries. However, since users only interact with the Inventory Items on the shipment they never actually see or use this Shipment Items so there's really no interaction with them; it's simply for the roll-up summaries. I needed a way to allow users to manage the Inventory Items on the shipment but in the background add/move/remove Shipment Items to keep the number of records in synch with the Inventory Items. Here is the trigger that I wrote for the Inventory Items to implement this functionality:
Trigger ShipmentItemProcess.cls
/**************************************************************************************
* Keeps inventory items and shipment items in sync. If an inventory item is on a
* shipment, then it ensures that there is a corresponding shipment item record. When
* an inventory item is removed from a shipment, it deletes the shipment item record.
**************************************************************************************/
trigger ShipmentItemProcess on Inventory_Item__c (after update, after insert) {
if (Trigger.isUpdate) {
List<inventory_Item__c> invItemsToInsert = new List<inventory_Item__c>();
Map<id,ID> mapInvItemShipment = new Map<id,ID>();
Set<id> invItemIdsToUpdate = new Set<id>();
Set<id> invItemIdsToDelete = new Set<id>();
// figure out which ones need to be inserted, updated or deleted
for (Integer i=0;i<trigger.new.size();i++) {
// if the old is null and the new is NOT null, they are assigning to a shipment - INSERT RECORD
if (Trigger.old[i].Shipment__c == null & Trigger.new[i].Shipment__c != null) {
invItemsToInsert.add(Trigger.new[i]);
// if old is NOT null and new is null, then they are removing from the shipment - DELETE RECORD
} else if (Trigger.old[i].Shipment__c != null & Trigger.new[i].Shipment__c == null) {
invItemIdsToDelete.add(Trigger.new[i].id);
// if they are both NOT null the we need to switch the new one to another shipment
} else if (Trigger.old[i].Shipment__c != null & Trigger.new[i].Shipment__c != null) {
if (Trigger.old[i].Shipment__c != Trigger.new[i].Shipment__c) {
mapInvItemShipment.put(Trigger.new[i].id,Trigger.new[i].Shipment__c);
invItemIdsToUpdate.add(Trigger.new[i].id);
}
}
}
// insert the new shipment records
if (invItemsToInsert.size() > 0) {
List<shipment_Item__c> shipmentItemsToInsert = new List<shipment_Item__c>();
for (Inventory_Item__c item : invItemsToInsert) {
Shipment_Item__c shipItem = new Shipment_Item__c();
shipItem.Name = item.Name;
shipItem.Inventory_Item__c = item.Id;
shipItem.Shipment__c = item.Shipment__c;
shipmentItemsToInsert.add(shipItem);
}
insert shipmentItemsToInsert;
}
// delete the corresponding shipment items that were removed
if (invItemIdsToDelete.size() > 0)
delete [select id from Shipment_Item__c where Inventory_Item__c IN :invItemIdsToDelete];
// update ones that have been moved to another shipment
if (invItemIdsToUpdate.size() > 0) {
List<shipment_Item__c> itemsToUpdate = [select Id, Inventory_Item__c, Shipment__c from Shipment_Item__c where Inventory_Item__c IN :invItemIdsToUpdate];
for (Shipment_Item__c item : itemsToUpdate)
item.Shipment__c = mapInvItemShipment.get(item.Inventory_Item__c);
update itemsToUpdate;
}
} else {
List<shipment_Item__c> shipmentItemsToInsert = new List<shipment_Item__c>();
for (Inventory_Item__c item : Trigger.new) {
if (item.Shipment__c != null) {
Shipment_Item__c shipItem = new Shipment_Item__c();
shipItem.Name = item.Name;
shipItem.Inventory_Item__c = item.Id;
shipItem.Shipment__c = item.Shipment__c;
shipmentItemsToInsert.add(shipItem);
}
}
if (shipmentItemsToInsert.size() > 0)
insert shipmentItemsToInsert;
}
}My test class looks like:
@isTest
private class Test_ShipmentItemProcess {
static ID createShipment(String shipmentName) {
Shipment__c shipment = new Shipment__c(
name = shipmentName
);
insert shipment;
return shipment.id;
}
static Inventory_Item__c createInventoryItem(String itemName) {
Inventory_Item__c item = new Inventory_Item__c(
name = itemName
);
insert item;
return item;
}
static testMethod void testInsertAndDelete() {
ID ship1Id = createShipment('Shipment 1');
Inventory_Item__c item1 = createInventoryItem('LP100');
// update the item with the new shipment number
item1.Shipment__c = ship1Id;
update item1;
// fetch the newly created shipment item and make sure it was created correctly
Shipment_Item__c shipItem1 = [select Id,Shipment__c,Inventory_Item__c from Shipment_Item__c where Inventory_Item__c = :item1.id];
System.assertEquals(item1.id,shipItem1.Inventory_Item__c);
System.assertEquals(item1.Shipment__c,shipItem1.Shipment__c);
// now delete the shipment
item1.Shipment__c = null;
update item1;
// make sure there are no records
System.assertEquals(0,[select count() from Shipment_Item__c where Inventory_Item__c = :item1.id]);
}
static testMethod void testChangeShipment() {
ID ship1Id = createShipment('Shipment 1');
Inventory_Item__c item = new Inventory_Item__c(
name = 'My LP',
Shipment__c = ship1Id
);
insert item;
Shipment_Item__c si = new Shipment_Item__c();
si.Inventory_Item__c = item.id;
si.Name = 'My LP';
si.Shipment__c = ship1Id;
insert si;
ID ship2Id = createShipment('Shipment 2');
item.Shipment__c = ship2Id;
update item;
// fetch the newly created shipment item and make sure it was created correctly
Shipment_Item__c shipItem2 = [select Id,Shipment__c,Inventory_Item__c from Shipment_Item__c where Inventory_Item__c = :item.id];
System.assertEquals(ship2Id,shipItem2.Shipment__c);
}
}
