Visualforce page: Add related records to custom object with custom button

Question

I would like to create a VF page ("AllUnitIdssaved") that will accept users inputs. This VF page is on the "Shipment_Details__c", which has a lookup to "QuoteLineItem". When the user clicks a custom button ("Create Unit Id") on the Shipment_Details related list, it should bring up the VF page.

A couple things I need help on:

1. I'm getting an error when I click the "Create Unit Id" button. Below is my setup for my custom button.

   Behavior: Display in existing window with sidebar
   Button or Link URL: window.location = '/apex/AllUnitIdssaved';

2. How do I link the Shipment_Details records that are being created on the Visualforce page to the Quote Line Item records? Here's my markup:

   <apex:page Controller="AddmultipleUnitIdsController">
       <apex:form >
           <apex:pageBlock >
               <apex:pageBlockTable value="{!listUnitId}" var="unit">
                   <apex:column headerValue="Create Unit Id">
                       <apex:inputField value="{!unit.Name}"/>
                   </apex:column>
               </apex:pageBlockTable>
               <apex:pageBlockButtons >
                   <apex:commandButton value="Create Unit Ids" action="{!addUnitId}"/>
                   <apex:commandButton value="Save Unit Ids" action="{!saveUnitId}"/>
               </apex:pageBlockButtons>
           </apex:pageBlock>
       </apex:form>
   </apex:page>
   

   Controller:

   public class AddmultipleUnitIdsController {
   
       Shipment_Detail__c unitid = new Shipment_Detail__c();
   
       public list<Shipment_Detail__c> listUnitId{ get; set; }
   
       public AddmultipleUnitIdsController()
       {
           listUnitId=new list<Shipment_Detail__c>();
           listUnitId.add(unitid);
       }
   
       Public void addUnitId()
       {
           Shipment_Detail__c unit = new Shipment_Detail__c();
           listUnitId.add(unit);
       }
   
       public PageReference saveUnitId() {
   
       for(Integer i=0; i<listUnitId.size(); i++)
       {
           insert listUnitId;
       }
           return Page.AllUnitIdssaved;
       }
   }
   

Answer 1

As for linking the new Shipment_Detail records to their parent QuoteLineItem record, you need to pass the QuoteLineItem's Id to the visualforce page in the querystring, like this:

https://test.salesforce.com/apex/myPageName?Id=myQuoteLineItemId

Then, in your page controller, you can get the Id value like this:

Id quoteLineItemId = apexPages.currentPage().getParameters().get('Id');

Use the Id to populate the lookup field for each new Shipment_Detail record.

Also, you should take your DML write out of the for loop. (This is a no-no!)

for(Integer i=0; i<listUnitId.size(); i++)
{
    insert listUnitId;
}

Since you can only have 150 DML operations (inserts, updates, deletes, ...) in a single transaction, you could easily use them all up if you inserted one record at a time!

Instead, you can insert your list of Shipment_Detail records all at once.

insert(listUnitId);