Hi -

I have created a custom component in an MXML file based on a VBox that
contains another custom component.
Something like below (I will call it CustomVBox for illustrative purposes):
<!-- file name CustomVBox.mxml -->
<mx:VBox>
<CustomRow>
</CustomRow>
</mx:VBox>

Now - in an action script file I wish to create the CustomVBox:
var comp:CustomVBox = new CustomVBox().

The problem is that the CustomRow inside the CustomVBox component is now a
public member that my action script can refer to, but calling the constructor
will not instantiate the sub component. So if I wanted to set some property on
the inner CustomRow object, I get a null reference exception.

If within my action script I addChild(comp) first, that creates the child
components and I am okay. However, I want to be able to set all my properties
up front. So I could just save off any settings and use them when
createChildren() is called. But the CustomRow, being an mxml tag in my
CustomVBox mxml file, is still public and nothing prevents a user from
accessing it directly and getting the null reference before createChildren()
got called.

How do I prevent this? Am I forced to write it all in actionscript so that my
subcomponent can be made private or can I still write it in mxml and prevent
the null reference exception?

Thank you,
Joel

You need to listen to flex event creationComplete, or override childrenCreated
protected UIComponent method to inform you on that occasion that all children
are created, or change creationPolicy to ContainerCreationPolicy.ALL (this will
ensure that children are built once you instantiate the component). However,
the last way isn't preferable because this will force your component into
creating children that may be invisible at the creation time.