internal对当前模块是私有的. fileprivate是当前文件(以前称为private)的专用文件.新的private在当前范围内是私有的(更接近于大多数人可能认为私有的范围).

internal is private to the current module. fileprivate is private to the current file (which used to be called private). The new private is private to the current scope (closer to what most people probably think of as private).