Method Does Not Exist error message

Question

My class subtracts the values of child account number fields from the current values of it's parent account number fields in a hierarchy. I need this class to run everytime a child account changes its parent (i.e the parent name field is edited to a new name). I'm attempting to have this trigger compare the old value and the new value of the parent field, when creating the logic for this trigger I keep recieving this error message:

Method does not exist or incorrect signature: void executeSub(Account) from the type Parent_Subtract

Class:

public class Parent_Subtract {
public static void executeSub(List<Account> scope) {

    Id CRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Customer Account').getRecordTypeId();
    Id DRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Division Account').getRecordTypeId();
    Id SRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Site Account').getRecordTypeId();
    Id ERecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Enterprise Account').getRecordTypeId();
    Id DSAccounts = '01270000578681Y';


        List<Id> listIds = new List<Id>();
        Map<Id, Account> parentAccounts = new Map<Id, Account>([SELECT Id, RecordTypeId, Parent_Account__c, Total_CCF__c, Total_Revenue__c, 
                                                                Total_Usage_kWh__c, Account_kw__c, AnnualRev FROM Account WHERE ID In :listIds]);
        Map<Id, Account> newParent = new Map<Id, Account>();
        Set<ID> setParentAcctID = new set<ID>();
        List<Account> listforFinalUpdate = new List<Account>();

    for(Account acc : scope){
        setParentAcctID.add(acc.Parent_Account__c);
    }

        List<account> listParentAcctData = [Select id, Total_CCF__c, Total_Revenue__c, 
                                                                Total_Usage_kWh__c, Account_kw__c, AnnualRevenue 
                                                                FROM account 
                                                                WHERE id =: setParentAcctID];
        for(Account a : listParentAcctData)
        {
            newParent.put(a.id,a);
        }

      for(Account acc: scope)
      {
        Account acct = newParent.get(acc.Parent_Account__c);

            system.debug('acc.Total_Usage_kWh__c:'+acc.Total_Usage_kWh__c);
            system.debug('acc.Total_CCF__c:'+acc.Total_CCF__c);
            system.debug('acc.AnnualRev:'+acc.AnnualRev);
            system.debug('acc.Account_kw__c:'+acc.Account_kw__c);

            acct.Total_Usage_kWh__c -= acc.Total_Usage_kWh__c;
            acct.Total_CCF__c -= acc.Total_CCF__c;
            acct.AnnualRev -= acc.AnnualRev;
            acct.Account_kw__c -= acc.Account_kw__c;

                listforFinalUpdate.add(acct);
        }               

        if(listforFinalUpdate.size() > 0)
        {
          update  listforFinalUpdate;
        }
    }

}

Trigger:

   if(Trigger.isUpdate){
        for(Account acc: Trigger.new){

            Account oldName = Trigger.oldMap.get(acc.Parent_Account__c);

            Account newName = Trigger.newMap.get(acc.Parent_Account__c);


                if(newName != oldName){
                      acct.add(acc);                                                                                                                                 
            }

        }
        Parent_Subtract.executeSub(acct);
    } 

   } 

Am I on the right track with this functionality and does anyone know why I am recieving this message?

Answer 1

You're calling a method with a single Account parameter:

Parent_Subtract.executeSub(acct);

but this method is defined to take a List<Account> as its parameter:

public static void executeSub(List<Account> scope) 

This method is bulkified: it is defined to run exactly one DML operation:

update  listforFinalUpdate;

regardless of how many Account records it receives. For this reason you need to be calling it with a List<Account>, not calling it repeatedly in a loop. Your trigger should accumulate a List<Account> inside your for loop, and then make a single call to executeSub() outside the loop.