File Handling
People shouldn’t need to think about the file system while creating, viewing, and manipulating files. If your app works with files, downplay file handling as much as possible.
当创建、浏览和操作文件时用户不应该需要考虑文件系统。如果你的app需要处理文件，尽量弱化文件处理过程。
Instill confidence that work is always preserved unless canceled or deleted.In general, don’t make people explicitly save files. Instead, save changes automatically at regular intervals, when opening and closing files, and when switching to another app. In some cases, such as while editing an existing file, save and cancel options may still make sense for the sake of confirming when the edits are actually captured.
持续灌输信心，除非取消或删除工作都会被保存。一般情况下，不要让用户显式保存文件。取而代之，在定期的间隔、当打开和关闭文件时、当转换到其他app时，自动保存改变。在一些情况下，例如当编辑一个存在的文件，当编辑器被捕获时，为了确认保存和取消选项也许仍然有用。
Don't provide an option to create local-only files.Users often expect all of their files to be available on all of their devices. Whenever possible, your app should support cloud-based file storage through a service such as iCloud.
不要提供一个选项来创建一个本地文件。用户通常期望文件再他们所有设备都是可用的。尽可能让你的app支持利用如iCloud等服务来创建基于云存储的文件。
Implement an intuitive and graphical file browsing interface.Ideally, use the system’s familiar document picker for browsing. If you implement a custom file browser, make sure it’s intuitive and efficient. File browsers work best when they’re highly graphical, providing visual representations of files. To speed navigation, minimize gestures, and consider providing a new document button, so people don’t need to go elsewhere to create a new document.
实现一个直观的、图形化的文件浏览界面。理想情况下，用系统熟悉的文件选择器来浏览。如果你实现一个定制的文件浏览器，确保它直观而高效。当文件浏览器高度图形化、提供文件可视化的呈现时最好用。为了加速浏览，减少手势，考虑提供一个新的文件按钮，所以用户不必去一个其他地方就能创建一个新的文件。
Let users preview files without leaving your app.You can use Quick Look to let people view the contents of Keynote, Numbers, and Pages documents, PDFs, images, and certain other types of files, even if your app doesn’t actually open them. SeeQuick Look.
不用离开你的应用就能预览文件。你可以用Quick Look让用户浏览Keynote, Numbers, and Pages documents, PDFs, images, and certain other types of files的内容，即使你的app不是真的打开他们。SeeQuick Look.
When appropriate, share files with other apps.If it makes sense, your app can share its files with other apps through adocument provider extension. Your app can also let people browse and open files from other apps. For developer guidance, seeDocument Picker Programming Guide.
合适时，和其他app分享文件。如果有意义，你的app可以通过document provider extension 与其他app分享文件。你的app可以让用户从其他app浏览和打开文件。For developer guidance, seeDocument Picker Programming Guide.