Grouping Collection separating numeric 5 from String "5"

BackGround: I have an advanced data grid. The data provider for this ADG is an ArrayCollection. There is a grouping collection on an ID field of this AC.

Example of a couple items within this AC the AC var name is "arcTemplates":

(mx.collections::ArrayCollection)#0
  filterFunction = (null)
  length = 69
  list = (mx.collections::ArrayList)#1
    length = 69
    source = (Array)#2
      [0] (Object)#3
        abbreviation = "sore-throat"
        insertDate = "11/16/2009"
        name = "sore throat"
        templateID = 234
        templateType = "New Problem"
        templateTypeID = 1
     [32] (Object)#35
        abbreviation = 123
        insertDate = "03/08/2010"
        name = 123
        templateID = 297
        templateType = "New Problem"
        templateTypeID = 1
     [55] (Object)#58
        abbreviation = 1234
        insertDate = "11/16/2009"
        name = 1234
        templateID = 227
        templateType = "Exam"
        templateTypeID = 5
     [56] (Object)#59
        abbreviation = "breast only"
        insertDate = "03/15/2005"
        name = "breast exam"
        templateID = 195
        templateType = "Exam"
        templateTypeID = 5

Example of Flex code leading to the Grouping:

<mx:AdvancedDataGrid displayItemsExpanded="true" id="gridTemplates">
  <mx:dataProvider>
    <mx:GroupingCollection id="gc" source="{arcTemplates}">
      <mx:Grouping >
        <mx:GroupingField name="templateTypeID" compareFunction="gcSort">

GC sort function:

public function gcSort(a:Object, b:Object):int{
    return ObjectUtil.stringCompare(String(a.templateTypeID + a.name).toLowerCase(), 
                                    String(b.templateTypeID + b.name).toLowerCase());
}

Problem: In my AC example there are a few items, items 0, 32 and 56 properly sort and group to their templateTypeID, but item 55 does something weird. It seems to sort/group on the numeric 5 instead of the string "5". Gets stranger. If I change the name property to contain text (so 1234x) it then correctly sorts/groups to the string "5"

Question: What is going on here and how do I fix it?

If i trust your trace, you see that name=1234 is written without quote, so it is considered as a Number.

When you are doing in your gcSort String(a.templateTypeID + a.name), you are in fact this time adding two numbers (5+1234) and convert them back to a String => "1239".

What you can do is convert first your name into string and then do your concatenation:

(a.templateTypeID + a.name.toString()).toLowerCase()