reference in visualforce the lookup field on child record in master detail

Question

<apex:pageBlockTable value="{!oldSubscriptionAndAsset}" var="assetAndSubs">
     <apex:column>
           <apex:facet name="header">Asset</apex:facet>
           <apex:outputText value="{!assetAndSubs.SBQQ__Asset__r.Name}"/>
     </apex:column>
     <apex:column>
           <apex:facet name="header">Asset</apex:facet>
           <apex:outputText value="{!assetAndSubs.SBQQ__Product__r.Name}"/>
     </apex:column> 
</apex:pageBlockTable>

oldSubscriptionAndAsset =[SELECT Id, SBQQ__Product__r.Name, SBQQ__Quantity__c,(SELECT Id, SBQQ__Asset__r.Name, SBQQ__Asset__r.SerialNumber, SBQQ__Asset__r.Is_Selected_For_Renewal__c  FROM SBQQ__SubscribedAssets__r) FROM SBQQ__Subscription__c];

I have a master detail relationship, Subscription(Master) and SubscribedAsset(Child), in my visualforce page, I want to show in different column the subscription name (master), name of the asset in lookup field Asset__c in SubscribedAsset(child record). So that, every subscription has many asset. My problem is, how could I reference the lookup fields of child records on different column? what will be the exact 'value' for the output text?

Answer 1

What's happening here is that each SBQQ__Subscription__c in oldSubscriptionAndAsset has a property SBQQ__SubscribedAssets__r, whose value is a List. What you are trying to reference is a property SBQQ__Product__r.Name on the objects contained in that list.

You cannot do that with oldSubscriptionAndAsset.SBQQ__Product__r.Name, because that is not a property of the type SBQQ__Subscription__c. You also cannot do oldSubscriptionAndAsset.SBQQ__SubscribedAssets__r.SBQQ__Product__r.Name, because oldSubscriptionAndAsset.SBQQ__SubscribedAssets__r is also a List.

To access this property, you must be iterating over the child objects in SBQQ__SubscribedAssets__r. You can do this in two ways, and it's not clear from your question which one is correct.

1. You can use a nested iteration, where you use an outer loop (probably an <apex:repeat>; you can't use an <apex:pageBlockTable> as an outer loop here) to iterate over the SBQQ__Subscription__c records in oldSubscriptionAndAsset. Then, you can use an inner loop, which could be an <apex:pageBlockTable>, to iterate over the list oldSubscriptionAndAsset.SBQQ__SubscribedAssets__r. Inside the inner iteration, you can access properties like SBQQ__Product__r.Name through its iteration variable.
2. If your Visualforce page is really only looking at the children of a single SBQQ__Subscription__c record, you can change your query. If you change the type of oldSubscriptionAndAsset from List<SBQQ__Subscription__c> to SBQQ__Subscription__c and query for exactly one record, you no longer need a nested iteration. you would then do

SBQQ__Subscription__c oldSubscriptionAndAsset = [SELECT Id, SBQQ__Product__r.Name, SBQQ__Quantity__c,(SELECT Id, SBQQ__Asset__r.Name, SBQQ__Asset__r.SerialNumber, SBQQ__Asset__r.Is_Selected_For_Renewal__c FROM SBQQ__SubscribedAssets__r) FROM SBQQ__Subscription__c WHERE Id = :SOME_ID LIMIT 1];

The value attribute on your <apex:pageBlockTable> would then be {! oldSubscriptionAndAsset.SBQQ__SubscribedAssets__r }, and your columns could directly reference properties of the child objects.