dd387a7aa2
* Revert "Address the real lifetime issue of the SDK's `Client` by making `Context.mediaProvider` weak. (#4466)"
This reverts commit b9d1558216.
* Better docs.
88 lines
3.9 KiB
Swift
88 lines
3.9 KiB
Swift
//
|
|
// Copyright 2022-2024 New Vector Ltd.
|
|
//
|
|
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
|
|
// Please see LICENSE files in the repository root for full details.
|
|
//
|
|
|
|
import Combine
|
|
import Foundation
|
|
|
|
/// A common ViewModel implementation for handling of `State` and `ViewAction`s. This original version
|
|
/// is implemented using SwiftUI's original `ObservableObject` and `@Published` pattern.
|
|
///
|
|
/// Generic type State is constrained to the BindableState protocol in that it may contain (but doesn't have to)
|
|
/// a specific portion of state that can be safely bound to.
|
|
/// If we decide to add more features to our state management (like doing state processing off the main thread)
|
|
/// we can do it in this centralised place.
|
|
@MainActor
|
|
class StateStoreViewModel<State: BindableState, ViewAction> {
|
|
/// For storing subscription references.
|
|
///
|
|
/// Left as public for `ViewModel` implementations convenience.
|
|
var cancellables = Set<AnyCancellable>()
|
|
|
|
/// Constrained interface for passing to Views.
|
|
var context: Context
|
|
|
|
var state: State {
|
|
get { context.viewState }
|
|
set { context.viewState = newValue }
|
|
}
|
|
|
|
init(initialViewState: State, mediaProvider: MediaProviderProtocol? = nil) {
|
|
context = Context(initialViewState: initialViewState, mediaProvider: mediaProvider)
|
|
context.viewModel = self
|
|
}
|
|
|
|
/// Override to handles incoming `ViewAction`s from the `ViewModel`.
|
|
/// - Parameter viewAction: The `ViewAction` to be processed in `ViewModel` implementation.
|
|
func process(viewAction: ViewAction) {
|
|
// Default implementation, -no-op
|
|
}
|
|
|
|
// MARK: - Context
|
|
|
|
/// A constrained and concise interface for interacting with the ViewModel.
|
|
///
|
|
/// This class is closely bound to`StateStoreViewModel`. It provides the exact interface the view should need to interact
|
|
/// ViewModel (as modelled on our previous template architecture with the addition of two-way binding):
|
|
/// - The ability read/observe view state
|
|
/// - The ability to send view events
|
|
/// - The ability to bind state to a specific portion of the view state safely.
|
|
/// This class was brought about a little bit by necessity. The most idiomatic way of interacting with SwiftUI is via `@Published`
|
|
/// properties which which are property wrappers and therefore can't be defined within protocols.
|
|
/// A similar approach is taken in libraries like [CombineFeedback](https://github.com/sergdort/CombineFeedback).
|
|
/// It provides a nice layer of consistency and also safety. As we are not passing the `ViewModel` to the view directly, shortcuts/hacks
|
|
/// can't be made into the `ViewModel`.
|
|
@dynamicMemberLookup
|
|
@MainActor
|
|
final class Context: ObservableObject {
|
|
fileprivate weak var viewModel: StateStoreViewModel?
|
|
|
|
/// Get-able/Observable `Published` property for the `ViewState`
|
|
@Published fileprivate(set) var viewState: State
|
|
|
|
/// An optional image loading service so that views can manage themselves
|
|
/// Intentionally non-generic so that it doesn't grow uncontrollably
|
|
let mediaProvider: MediaProviderProtocol?
|
|
|
|
/// Set-able/Bindable access to the bindable state.
|
|
subscript<T>(dynamicMember keyPath: WritableKeyPath<State.BindStateType, T>) -> T {
|
|
get { viewState.bindings[keyPath: keyPath] }
|
|
set { viewState.bindings[keyPath: keyPath] = newValue }
|
|
}
|
|
|
|
/// Send a `ViewAction` to the `ViewModel` for processing.
|
|
/// - Parameter viewAction: The `ViewAction` to send to the `ViewModel`.
|
|
func send(viewAction: ViewAction) {
|
|
viewModel?.process(viewAction: viewAction)
|
|
}
|
|
|
|
fileprivate init(initialViewState: State, mediaProvider: MediaProviderProtocol?) {
|
|
self.viewState = initialViewState
|
|
self.mediaProvider = mediaProvider
|
|
}
|
|
}
|
|
}
|