Classswift-composable-architecture 1.18.0ComposableArchitecture

ViewStore

A ViewStore is an object that can observe state changes and send actions. They are most commonly used in views, such as SwiftUI views, UIView or UIViewController, but they can be used anywhere it makes sense to observe state or send actions.

ViewStore.swift:94 ViewStore.md

iOS: deprecated
macOS: deprecated
tvOS: deprecated
watchOS: deprecated

@dynamicMemberLookup @preconcurrency @MainActor final class ViewStore<ViewState, ViewAction>

Mangled symbol

s22ComposableArchitecture9ViewStoreC What are these?

FNV24 hash: 1OEYC

In SwiftUI applications, a ViewStore is accessed most commonly using the WithViewStore view. It can be initialized with a store and a closure that is handed a view store and returns a view:

var body: some View {
  WithViewStore(self.store, observe: { $0 }) { viewStore in
    VStack {
      Text("Current count: \(viewStore.count)")
      Button("Increment") { viewStore.send(.incrementButtonTapped) }
    }
  }
}

View stores can also be observed directly by views, scenes, commands, and other contexts that support the @ObservedObject property wrapper:

@ObservedObject var viewStore: ViewStore<State, Action>

In UIKit applications a ViewStore can be created from a Store and then subscribed to for state updates:

let store: Store<State, Action>
let viewStore: ViewStore<State, Action>
private var cancellables: Set<AnyCancellable> = []

init(store: Store<State, Action>) {
  self.store = store
  self.viewStore = ViewStore(store, observe: { $0 })
}

func viewDidLoad() {
  super.viewDidLoad()

  self.viewStore.publisher.count
    .sink { [weak self] in self?.countLabel.text = $0 }
    .store(in: &self.cancellables)
}

@objc func incrementButtonTapped() {
  self.viewStore.send(.incrementButtonTapped)
}

Creating a view store

init<State, Action>(Store<State, Action>, observe: @escaping (_ state: State) -> ViewState, send: @escaping (_ viewAction: ViewAction) -> Action, removeDuplicates: @escaping (_ lhs: ViewState, _ rhs: ViewState) -> Bool)
Initializes a view store from a store which observes changes to state.
init<State>(Store<State, ViewAction>, observe: @escaping (_ state: State) -> ViewState, removeDuplicates: @escaping (_ lhs: ViewState, _ rhs: ViewState) -> Bool)
Initializes a view store from a store which observes changes to state.
init<State, Action>(Store<State, Action>, observe: @escaping (_ state: State) -> ViewState, send: @escaping (_ viewAction: ViewAction) -> Action)
Initializes a view store from a store which observes changes to state.
init<State>(Store<State, ViewAction>, observe: @escaping (_ state: State) -> ViewState)
Initializes a view store from a store which observes changes to state.
typealias ViewStoreOf<R>
A convenience type alias for referring to a view store of a given reducer’s domain.

Accessing state

var state: ViewState
The current state.
subscript<Value>(dynamicMember: KeyPath<ViewState, Value>) -> Value
Returns the resulting value of a given key path.

Sending actions

func send(ViewAction) -> StoreTask
Sends an action to the store.
func send(ViewAction, while: @escaping (_ state: ViewState) -> Bool) async
Sends an action into the store and then suspends while a piece of state is true.
func yield(while: @escaping (_ state: ViewState) -> Bool) async
Suspends the current task while a predicate on state is true.

SwiftUI integration