Related List button not working with Contoller extension code

Question

I've been struggling with the following problem for a few days now...

What I want to do: I'm trying to create a visual force page and controller to 'swap' 2 fields when a list button 'Swap Decscriptions' is clicked. The solution is partially working, I have created a VF page and controller class to handle the button click, but I'm having some issues with accessing the data properly.

The objects involved are all custom: Sales_Order__c -> Sales_Order_line__c -> Item__c

Once the Sales Order page is opened I added a button to the Sales Order Line related list. When the Swap button is clicked the Amazon_CAD_Item__c and Flow_CAD_Item__c are to be swapped for all lines.

Amazon_CAD_Item__c and Flow_CAD_Item__c are Lookups to the Item Object. A self-reference I guess, and what I seem to have a lot of trouble with.

VF Page:

 <apex:page standardController="PBSI__PBSI_Sales_Order__c" extensions="SwapFieldsController" action="{!swapFields}">
</apex:page>

Apex Class:

public class SwapFieldsController {

    private ApexPages.StandardController stdCtrlr;
    
     public SwapFieldsController(apexpages.StandardController inStd)
    {
            stdCtrlr = inStd;
        
        
    }
    
    public PageReference swapFields()
    {
        
        PBSI__PBSI_Sales_Order__c salesObj = (PBSI__PBSI_Sales_Order__c)stdCtrlr.getRecord();
        ID salesOrderId =  salesObj.Id;
       
        system.debug('SO Id:' +salesOrderId);
        
        
        PBSI__PBSI_Sales_Order__c soList = [select id, name, (select name, PBSI__Item__c from PBSI__Sales_Order_Lines__r) from PBSI__PBSI_Sales_Order__c where id = :salesOrderId];
        
        list<PBSI__PBSI_Sales_Order_Line__c> lineList = soList.PBSI__Sales_Order_Lines__r;
        system.debug('order line list:' +lineList);
        for(PBSI__PBSI_Sales_Order_Line__c ol : lineList){
            
            List<PBSI__PBSI_Item__c> updateItemList = new List<PBSI__PBSI_Item__c>();
            PBSI__PBSI_Item__c item = new PBSI__PBSI_Item__c(id=ol.PBSI__ITEM__c); //item Nevers seems to get instantiated
            
         // all of the data below return nulls...
            system.debug('Item Object:' +item);

            string tmp = item.Amazon_CAD_Item__c;           
            
            system.debug('tmp:' +tmp);
            system.debug('Amazon:' +item.Amazon_CAD_Item__c);
            system.debug('Flow:' +item.Flow_CAD_Item__c);            
                                
            //update item;
            
        }
              
        
        return stdCtrlr.view();
    }

}

Any help or insights are appreciated. I am also open to different ways of approaching a solution for this. Thanks in advance!

Answer 1

When you instantiate an sObject variable with the Id of an existing record:

        PBSI__PBSI_Item__c item = new PBSI__PBSI_Item__c(id=ol.PBSI__ITEM__c); //item Nevers seems to get instantiated
        

It does not inherit field values from the source variable or record, so this:

     // all of the data below return nulls...
        system.debug('Item Object:' +item);

        string tmp = item.Amazon_CAD_Item__c;           
        
        system.debug('tmp:' +tmp);
        system.debug('Amazon:' +item.Amazon_CAD_Item__c);
        system.debug('Flow:' +item.Flow_CAD_Item__c);            

is the expected outcome.

If you want the new record to inherit fields, make sure to query the fields you want, and then clone the record:

    PBSI__PBSI_Sales_Order__c soList = [select id, name, (select name, PBSI__Item__r.Amazon_CAD_Item__c, PBSI__Item__r.Flow_CAD_Item__c from PBSI__Sales_Order_Lines__r) from PBSI__PBSI_Sales_Order__c where id = :salesOrderId];

// ...

item = ol.PBSI__Item__r.clone(true, false, false, false);

// Change field values and run update.