TriggerHandler Question about New/ Old Values

Question

I am trying to compare the 'old' value with the 'new' value on a record after it is updated using a TriggerHandler. Below is my code for the TriggerHandler class and also the Trigger.

Specifically, I am trying to update the Account name when a checkbox field on the Account is changed. This checkbox is updated by a Trigger on the AccountContactRelation, which is why I am trying to keep it in the same trigger.

I have been trying to test this but for some reason cannot get it working. I also added some system.debug() methods earlier and these are not triggering either in my debug logs. Am I doing something wrong here? Thank you.

public void updateHHDefaultTeam(List<AccountContactRelation> newList, Map<Id, AccountContactRelation> oldMap) {

        Set<Id> accountIdsToUpdate = new Set<Id>();
        
        for (AccountContactRelation acr : newList) {
            Account relatedAccount = [SELECT Id, Client_Household__c FROM Account WHERE Id = :acr.AccountId];
            
            if (oldMap.get(acr.Id).Account.Client_Household__c != acr.Account.Client_Household__c) {
                accountIdsToUpdate.add(relatedAccount.Id);
            }    
        }
        
        if (!accountIdsToUpdate.isEmpty()) {
            List<Account> accountsToUpdate = [SELECT Id, Name FROM Account WHERE Id IN :accountIdsToUpdate];
            for (Account a : accountsToUpdate) {
                a.Name = 'Test123';
            }
            update accountsToUpdate;
        }
        
    }

Here is the Trigger:

 trigger AccountContactRelationTrigger on AccountContactRelation (after insert, after update, after delete) {
   AccountContactRelationTriggerHandler();
   AccountContactRelTriggerHandler handler = new AccountContactRelTriggerHandler();

 switch on Trigger.OperationType  {
        when AFTER_UPDATE{
            handler.updateHHDefaultTeam(Trigger.new, Trigger.oldMap);

        }

Answer 1

In the trigger context, you can reach only fields from the processed object level. This means no relation fields are available. So parent fields are not available to compare unless we query it using a SOQL.

Also, If you want to track the changes for the field Account.Client_Household__c then you might need to shift your trigger to the Account object. You will not be able to track the account field changes on the AccountContactRelation object.