To loop an array with XTemplate in sencha touch 2.1.0

To loop an array with XTemplate in sencha touch 2.1.0

The Ext.XTemplate Docs says:
The tpl tag and the for operator are used to process the provided data
object:
If the value specified in for is an array, it will auto-fill, repeating
the template block inside the tpl tag for each item in the array.
If for="." is specified, the data object provided is examined.
While processing an array, the special variable {#} will provide the
current array index + 1 (starts at 1, not 0).
I follow the first rule and assign the data config of a panel with an
array of objects,but it just shows a blank.The code is as below:
{
xtype : 'panel',
tpl : new Ext.XTemplate([
'<tpl>',
'<div>',
'{index}',
'</div>',
'</tpl>'
]),
data : [
{index : '11'},
{index : '12'},
{index : '13'}
]
}
So i follow the second rule and add a 'for="."' for the '<tpl>',it works!
So,i want to know whether it really means you have to add a 'for="."' if
you just want to loop an array with Ext.XTemplate ?