# Earthquakes: Using a private-queue context to fetch data in background
This sample demonstrates how to set up a Core Data stack with NSPersistentContainer and use a private-queue context to import data on iOS and macOS.
NSFetchedResultsController, which is newly avaiable on macOS 10.12 but extensively adopted on iOS, is used as the data source of NSTableView. How to do batch deletes with NSBatchDeleteRequest is also covered in this sample.
Note that the data locates in a remote server that is out of our control and does not offer a secure communication channel, we'll use the http version of the URL and add "earthquake.usgs.gov" to the "NSExceptionDomains" value in the info.plist of this sample. When you commmunicate with your own servers, or when the services you use offer a secure communication option, you should always prefer to use HTTPS.
Xcode 9 or later, macOS 10.13 SDK or later.
Xcode 9 or later, iOS 11 SDK or later.
macOS 10.13 or later.
iOS 11 or later.
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