如何使用coredata获取按距离排序的地点列表

I have a coredata based iphone app and have an Entity that has latitude and longtitude as properties. How can I return all my entities ordered by distance from the current location? I previosuly did this without coredata writing a sql query, but am new to coredata and can't figure it out. I would like to use the NSFetchedResultsController to pass straight to my tableview.I have a coredata based iphone app and have an