swift - 私有访问权限

如图：

屏幕快照 2018-09-26 下午2.29.47.png

代码：

private typealias DidSelectedItemBlock = (_ atIndexPath:IndexPath, _ modelGroup:BGGroup,_ modelBGImage:BGImage) -> ()
var didSelectedItemBlock:DidSelectedItemBlock!

报错：
error：Property must be declared private because its type uses a private type

说明类型是私有的声明的该类型的变量也必须是私有的。