Core Data: Beyond the Basics

Jul 26 2022 · Swift 5.5, iOS 15, Xcode 13.3.1

Part 1: Fetching & Displaying Launches

08. Compound Predicates

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Previous episode: 07. Adding Launches to Lists Next episode: 09. Challenge - Adding Tags

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Instead of working with relationships another way you can fetch the launches for a particular list is by using something you’re already familiar with - predicates.

static func launches(in list: RocketLaunchList) -> FetchRequest<RocketLaunch> {}
let nameSortDescriptor = NSSortDescriptor(key: "name", ascending: true)
let launchDateSortDescriptor = NSSortDescriptor(key: "launchDate", ascending: false)
let listPredicate = NSPredicate(format: "%K == %@", "list.title", list.title!)
let isViewedPredicate = NSPredicate(format: "%K == %@", "isViewed", NSNumber(value: false))
let combinedPredicate = NSCompoundPredicate()
let combinedPredicate = NSCompoundPredicate(andPredicateWithSubpredicates: [listPredicate, isViewedPredicate])
return FetchRequest(entity: RocketLaunch.entity(),
  sortDescriptors: [nameSortDescriptor, launchDateSortDescriptor],
  predicate: combinedPredicate)
var launchesFetchRequest: FetchRequest<RocketLaunch>
init(launchList: RocketLaunchList) {
	self.launchList = launchList
	self.launchesFetchRequest = RocketLaunch.launches(in: launchList)
ForEach(launches, id: \.self) { launch in }