The treeReader property adds columns to the colModel property of the basic grid.

Syntax:

treeReader: [ 
    {property1:'value1'},
    {property2:'value2'},
    {...},
     ...
  ]

These properties, in alphabetic sequence, are the following:

Property	Type	Description	Default
expanded_field	string	true or false tells us if the tree at this level should be expanded when read from grid. If this field is true, child nodes should also be sent to the grid.	false
leaf_field	string	true or false
left_field	numeric
level_field	numeric
right_field	numeric

It is important to note here that the data returned from the server should be sorted in an appropriate way; for example

SELECT category_name, level, lft, rgt FROM categories ORDER BY lft;

leaf_field is easy in a Nested set model since

if( rgt == lft+1 ) isLeaf = true; else isLeaf = false;