Apex trigger to feed custom account lookup from Opportunity Product to Assets. Invalid foreign key relationship error

Question

We are using the Opportunity Products to Assets app (https://appexchange.salesforce.com/listingDetail?listingId=a0N30000001yKgpEAE) to create assets from opportunity products on closed/won opportunities. I am looking to amend the Apex Trigger component that passes the Account ID from the Opportunity to the Asset.

Our business is a broker, so we have 2 account record types that are attached to an opportunity. The customer account owns the opportunity but we then attach a partner/supplier account to the opportunity product via a custom lookup field. The above app passes the account that owns the opportunity ( the customer in our case) to the asset. We instead would like the partner account ID from the opportunity product (named Operator__c in our org) to be passed over as the owner of the asset.

Below is the standard component from the app with my amendments in bold. I have amended the Account.Id = portion of the below component to reference the opportunity line item Operator__c field but it is not working. I receive the following error –

Error: Compile Error: Invalid foreign key relationship: OpportunityLineItem.Operator__c

Trigger:

trigger CreateAssetonClosedWon on Opportunity (after insert, after update) {
 for(Opportunity o: trigger.new){ 
  if(o.isWon == true && o.HasOpportunityLineItem == true){
     String opptyId = o.Id;
     OpportunityLineItem[] OLI = [Select **Operator__c**, UnitPrice, Quantity, PricebookEntry.Product2Id, PricebookEntry.Product2.Name, Description, Converted_to_Asset__c  
                                  From OpportunityLineItem 
                                  where OpportunityId = :opptyId  and Converted_to_Asset__c = false];
     Asset[] ast = new Asset[]{};
     Asset a = new Asset();
     for(OpportunityLineItem ol: OLI){
        a = new Asset();
    **a.AccountId = ol.Operator__c.Id;**
        a.Product2Id = ol.PricebookEntry.Product2Id;
        a.Quantity = ol.Quantity;
        a.Price =  ol.UnitPrice;
        a.PurchaseDate = o.CloseDate;
        a.Status = 'Purchased';
        a.Description = ol.Description;
        a.Name = ol.PricebookEntry.Product2.Name;
        ast.add(a);
        ol.Converted_to_Asset__c = true;
   }
   update OLI; 
   insert ast;
  }
 }
}

Answer 1

If Operator__c holds partner account Id then use,

a.AccountId = ol.Operator__c;

In your code a.AccountId = ol.Operator__c.Id if you try to use relationship then use __r.Id instead of __c.id