NullPointerException: Attempt to de-reference a null object in a batchclass

Question

I have this batchclass with which I want to update some checkboxes on account with the values of related assets checkbox values. When running the class I get an System.NullPointerException: Attempt to de-reference a null object error.

I did some research and this could be because of a null value. I made a check on all of my fields but still get this error at the following line:

asst.account.Actief_onderhoud_Design_Solutions__c = asst.design_Solutions_Product__c;

Class

    global class BatchUpdateAccountByAsset implements
Database.Batchable<sObject>, Database.Stateful {        
    global Database.QueryLocator start(Database.BatchableContext bc) {
        return Database.getQueryLocator (
            [SELECT account.Name, design_Solutions_Product__c, layertec_Product__c, simuleon_Product__c, account.Actief_onderhoud_Design_Solutions__c,
             account.Actief_onderhoud_Layertec__c, account.Actief_onderhoud_Simuleon__c
             FROM Asset 
             WHERE (design_Solutions_Product__c = true AND account.Actief_onderhoud_Design_Solutions__c = false) 
                    OR (layertec_Product__c = true AND account.Actief_onderhoud_Layertec__c  = false)
                    OR (simuleon_Product__c = true AND account.Actief_onderhoud_Simuleon__c = false)
             ]);        
    }
    global void execute(Database.BatchableContext bc, List<Asset> scope){        
        List<Account> acc = new List<Account>();
        if(scope.size()!=Null){
            for (Asset asst : Scope) {
                if(asst.design_Solutions_Product__c !=null && asst.account.Actief_onderhoud_Design_Solutions__c !=null) {
                    asst.account.Actief_onderhoud_Design_Solutions__c = asst.design_Solutions_Product__c;
                }
                if(asst.layertec_Product__c !=null && asst.account.Actief_onderhoud_Layertec__c !=null) {
                    asst.account.Actief_onderhoud_Layertec__c = asst.layertec_Product__c;
                    }
                if(asst.layertec_Product__c !=null && asst.account.Actief_onderhoud_Simuleon__c !=null) {
                    asst.account.Actief_onderhoud_Simuleon__c = asst.simuleon_Product__c;
                    }
                acc.add(asst.account);
            } 
            update acc;
        }
    }

Answer 1

You can't directly set these parent fields from the Asset record.

You have to query for the related Account and set it's Actief_onderhoud_Design_Solutions__c directly.

So you'll prob need to do another query on all the Account ids, put that result in a map and get the related Account that way.

Also, there is no need to perform a null check here:

if(scope.size()!=Null){

You sometimes might need to do something like:

if(scope!= null && scope.size() > 0){

But the loop won't start if there is nothing in scope