Custom Roll up Trigger Exception Handling

Question

I have a two Parent objects. There is a junction between these two objects (not via master detailed but lookup).

I need to implement a custom rollup of these child records on the parent object.

In the trigger logic i do the following:

trigger on Child_Object ( before insert ) {
    helper(trigger.new);
}

Below is the helper logic:

helper(list<childObject> childlist) {

    list<Id> parentID = new list<ID>();
    // DO SOME PROCESSING HERE.
    for ( childObject cvar : childlist ) {
        parentId.add(cvar.parent_lookup__c);
    }
    // I HAVE DONE SOME PROCESSING ON THE PARENT RECORD ROLLUP AND UPDATING PARENT RECORDS.

    IF (parentList.size() > 0)
        update(parentList);
}

I am having a validation on the Parent that is restricting the update, which should not allow insertion of the child and fail the child records.

Unfortunately, I am unable to capture the error in the helper class using try and catch and show exception message on the child record on creation.

Could you please help me form a solution for the same.

Even tried using "database.SaveResult[]", but this fails since I am unable to capture the child reference in the saveResult as the action I update the parent and parent records fail.

How do i find the corresponding child that is causing the error.

TIA.

Answer 1

Your trigger is shown as a before insert trigger. I think that's a large part of your problem. If you stop and think about it, you can't really update a "roll-up" on records before the new record exists can you? If you can, I don't really see how. At a minimum, this needs to be an after insert trigger.

Only after the record has been inserted can you actually update the roll-up. If you want to use some custom visualforce, you could show "what it would be" on a visualforce page before inserting the new record, but you can't really update the field until the new records that support it exist.