SwiftUI immutable ViewStore

viewstore.swift

/// ViewStore acts as a state container, typically for some view over the application's central store.
/// You construct a ViewStore and pass it to a subview. Because it is Equatable, you can
/// make the subview Equatable as well, with `.equatable()`. The subview will then only render
/// when the actual value of the state changes.
struct ViewStore<LocalState, LocalAction>: Equatable
    where LocalState: Equatable {
    static func == (
        lhs: ViewStore<LocalState, LocalAction>,
        rhs: ViewStore<LocalState, LocalAction>
    ) -> Bool {
        lhs.state == rhs.state
    }
    
    let state: LocalState
    let send: (LocalAction) -> Void
}

/// Creates a tagged send function that can be used in a sub-view.
/// The returned send function will tag local view actions on the way out.
func address<Action, LocalAction>(
    send: @escaping (Action) -> Void,
    tag: @escaping (LocalAction) -> Action
) -> (LocalAction) -> Void {
    return { localAction in
        send(tag(localAction))
    }
}