reader

In server response there is property, in which all data.
To change it's name do this.

Example: Dynamic loading from server

{
  index: 'country',
  title: 'Country',
  type: 'combo',
  data: {
    proxy: {
      url: 'countries.php',
      method: 'POST',
      params: {
        region: 'europe'
      },
	  reader: {
	    root: 'items'
	  }
    }
  }
}
...
countries.php
{"items": ["UK", "Germany", "France"]}

Returned data from server must be valid JSON, in other case it will not be rendered

Default

'data'