EXTJS grid.column.renderer绑定失效

items:[{
	xtype: 'grid',
	itemConfig: {
	    viewModel: {},
	    controller: {}
	},
	columns: [{
		renderer: 'clmnRenderer'
	}]
}],
...
controller: {
	clmnRenderer: function(value){return value;}
}

Uncaught Error: No method named "clmnRenderer" on Ext.app.ViewController