<cfcomponent displayname="Parent" persistent="true"> ... <cfproperty name="totalFundingApproved" formula="select sum(ch.approved_amount) from child ch where ch.parent_id = id" /> ... </cfcomponent>
I'm using Ajax to persist records, and then I am returning the parent object to my callback function so I can then parse the object and update the UI with the new values. The super-simplified service method would like like this:
var parent = entityLoadByPK('Parent', arguments.id); child = parent.getChild(); child.setTotalFundingApproved(arguments.approvedAmount); entitySave(parent); return parent;
Now, it would be silly for ColdFusion to reload the values on the calculated property every time we ask for it. The problem is, I need it to be updated when the child is updated! There are a few things we could do to get the functionality we want. First, we can move the computed property out into a method call:
<cffunction name="getTotalFundingApproved" access="public" returntype="query" output="false"> <cfset var q = '' /> <cfquery name="q" datasource="#dsn#"> select sum(ch.approved_amount) from child ch where ch.parent_id = #getID()# </cfquery> <cfreturn q /> </cffunction>
The problem with that in my specific case is that I need to be able to sort on that property, and no matter how hard you try, you just can't sort on a method ;) Another option is to create a method like getTotalFundingApproved(). This seems kludgy to me. With proper documentation it could work, but you could have two possible values for the same property at any given time depending on the child collection's state.
I ended up reloading the object and returning that copy. To ensure a fresh read I'm using the ORMClearSession() method:
ormclearsession(); var parent = entityLoadByPK('Parent', id); return parent;
This works, but I'd love to see a way to trigger a reload of the computed property that I could use in the preUpdate() or preInsert() event handlers.
Update (2/22/2011): I was looking through the new functions in CF 9 today and found entityReload(). This could be used instead of ormClearSession(). ormClearSession() worked for me here since no other objects were in the session at the time. In other cases, entityReload() just makes more sense.