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使用 NSContactsUsageDescription 获取联系人列表时，出现以下错误。
This app has crashed because it attempted to access privacy-sensitive data without a usage description. The app's Info.plist must contain an NSContactsUsageDescription key with a string value explaining to the user how the app uses this data.
另外，在 swift 中获取整个联系人列表需要很长时间，而在 swift 3 中会出现此错误。