Structure

FetchedResults

A collection of results retrieved from a Core Data store.

Declaration 宣言

struct FetchedResults<Result> where Result : NSFetchRequestResult

Overview 概要

Use a FetchedResults instance to show or edit Core Data managed objects in your app’s user interface. You request a particular set of results by specifying a Result type as the entity type, and annotating the fetched results property declaration with a FetchRequest property wrapper. For example, you can create a request to list all Quake managed objects that the Loading and Displaying a Large Data Feed sample code project defines to store earthquake data, sorted by their time property:

@FetchRequest(sortDescriptors: [SortDescriptor(\.time, order: .reverse)])
private var quakes: FetchedResults<Quake>

The results instance conforms to RandomAccessCollection, so you access it like any other collection. For example, you can create a List that iterates over all the results:

List(quakes) { quake in
    NavigationLink(destination: QuakeDetail(quake: quake)) {
        QuakeRow(quake: quake)
    }
}

When you need to dynamically change the request’s predicate or sort descriptors, set the result instance’s nsPredicate and sortDescriptors or nsSortDescriptors properties, respectively.

The fetch request and its results use the managed object context stored in the environment, which you can access using the managedObjectContext environment value. To support user interface activity, you typically rely on the viewContext property of a shared NSPersistentContainer instance. For example, you can set a context on your top level content view using a container that you define as part of your model:

ContentView()
    .environment(
        \.managedObjectContext,
        QuakesProvider.shared.container.viewContext)

Topics 話題

Configuring the Associated Fetch Request

var nsPredicate: NSPredicate?

The request’s predicate.

var sortDescriptors: [SortDescriptor<Result>]

The request’s sort descriptors, accessed as value types.

Available when Result inherits NSManagedObject. ResultがNSManagedObjectを継承する場合に利用可能です。

var nsSortDescriptors: [NSSortDescriptor]

The request’s sort descriptors, accessed as reference types.

Getting Indices

var startIndex: Int

The index of the first entity in the results collection.

var endIndex: Int

The index that’s one greater than the last valid subscript argument.

Subscripts 添え字

subscript(Int) -> Result

Gets the entity at the specified index.

Type Aliases 型エイリアス

typealias Element

A type representing the sequence’s elements. シーケンスのもつ要素それらを表しているある型。

typealias Index

A type that represents a position in the collection. ある型、それはコレクションの中のある位置を表します。

typealias Indices

A type that represents the indices that are valid for subscripting the collection, in ascending order. ある型、それはインデックスそれらを表します、それらは昇順でコレクションに添え字をつけるために有効なものです。

typealias Iterator

A type that provides the collection’s iteration interface and encapsulates its iteration state. ある型、それはコレクションのもつ反復インターフェイスを提供およびそれの反復状態をカプセル化します。

typealias SubSequence

A collection representing a contiguous subrange of this collection’s elements. The subsequence shares indices with the original collection.