I have a 2 component.  I want to send the attribute value from the parent to child.  The attribute value is update after a record is created(I am pulling the record id back to the component).  But the attribute value shows undefined when use the second componen so that tells me that the attribute value is not getting updated.
I am referencing the second compont like this

<c:childcmp pcmpId="{!v.parentid}"/>

The child comp needs the parent id so whatever is the best way to get the parent id to the child component please advise.  I have tried events and have been not been succesful.
Thanks,
P