核心数据：什么时候用[refreshObject：obj mergeChanges：NO]“释放”未使用的NSManagedObjects？

I'm working on my first Core Data project, basing the NSManagedObjectModel development stage on Xcode's (Universal) Master-Detail template. The store based upon the ObjectModel is already populated with instances of various objects.I'm working on my first Core Data project, basi