I'm trying to build a VF component that references an attribute that is an instance of a child class. I have a top level class A and inner class B and C which extend class A and i am trying to pass the visualforce component instance of class B. Since only top level classes can be passed to component i have declared the attribute as of type A and i am passing instance of class b to the component. But i am getting this error "Cannot convert the value of '{!classA}' to the expected type. " My question is can we pass child instances to component.

Visualforce Component

<apex:component controller="ComponentController">

    <apex:attribute name="list" 
        description="" />

      <!--Some Code-->

Component Controller

public with sharing class ComponentController{
    public List<SObjectWrapper> sobjectWrappers {

Visualforce Page

<apex:page controller="DemoController">
    <apex:form >
        <apex:repeat value="{!mapWrapper}" var="item">
          <c:DynamicTable list="{!mapWrapper[item]}" />

Page Controller

public with sharing class DemoController {

    public Map<ParentNode,List<LevelOneNode>> mapWrapper{
        get ;
        set ;
  // Some Code which populates the list

Base Class

public abstract class SObjectWrapper implements Comparable {
    // Some Code

Child Class

public class ParentNode extends SObjectWrapper {
    public List<LevelOneNode> levelOneNodes {
   // Some Code

public class LevelOneNode extends SObjectWrapper {
         // Some Code

Also, if i directly pass instance of an child list the code is working, so the issue seems to be coming while iterating over map.

  • If B extends A and if B is declared as a top level class, then you can definitely pass to the component. Inner classes are more problematic - see salesforce.stackexchange.com/questions/15872/… – cropredy Oct 8 '14 at 17:05
  • i refactored my inner class to top level class but the same issue is occurring. – anmrk Oct 8 '14 at 17:52
  • Hmm - I have made this work so you should post the relevant component, invoking page, controller property, base class, and extension class bits of your issue to your original post - strip out all but the most essential bits so as not to 'code dump' on us :-) – cropredy Oct 8 '14 at 18:11

No you can't pass the child instance to a component attribute. We also ran into this same issue some time back and found the only solution is to declare the child instance class as a separate standalone class.

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