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Refactor vm context (#769)

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Alfonso Grillo 2023-04-05 19:19:05 +02:00 committed by GitHub
parent 063665d05c
commit 9998fadd3b
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2 changed files with 48 additions and 55 deletions
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99
ElementX/Sources/Other/SwiftUI/ViewModel/StateStoreViewModel.swift
View File

@ -17,49 +17,6 @@
import Combine
import Foundation
/// 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
class ViewModelContext<ViewState: BindableState, ViewAction>: ObservableObject {
fileprivate let viewActions: PassthroughSubject<ViewAction, Never>
/// Get-able/Observable `Published` property for the `ViewState`
@Published fileprivate(set) var viewState: ViewState
/// An optional image loading service so that views can manage themselves
/// Intentionally non-generic so that it doesn't grow uncontrollably
let imageProvider: ImageProviderProtocol?
/// Set-able/Bindable access to the bindable state.
subscript<T>(dynamicMember keyPath: WritableKeyPath<ViewState.BindStateType, T>) -> T {
get { viewState.bindings[keyPath: keyPath] }
set { viewState.bindings[keyPath: keyPath] = newValue }
}
init(initialViewState: ViewState, imageProvider: ImageProviderProtocol?) {
self.viewActions = PassthroughSubject()
self.viewState = initialViewState
self.imageProvider = imageProvider
}
/// Send a `ViewAction` to the `ViewModel` for processing.
/// - Parameter viewAction: The `ViewAction` to send to the `ViewModel`.
func send(viewAction: ViewAction) {
viewActions.send(viewAction)
}
}
/// A common ViewModel implementation for handling of `State` and `ViewAction`s
///
/// Generic type State is constrained to the BindableState protocol in that it may contain (but doesn't have to)
@ -68,8 +25,6 @@ class ViewModelContext<ViewState: BindableState, ViewAction>: ObservableObject {
/// we can do it in this centralised place.
@MainActor
class StateStoreViewModel<State: BindableState, ViewAction> {
typealias Context = ViewModelContext<State, ViewAction>
/// For storing subscription references.
///
/// Left as public for `ViewModel` implementations convenience.
@ -77,7 +32,7 @@ class StateStoreViewModel<State: BindableState, ViewAction> {
/// Constrained interface for passing to Views.
var context: Context
var state: State {
get { context.viewState }
set { context.viewState = newValue }
@ -85,13 +40,7 @@ class StateStoreViewModel<State: BindableState, ViewAction> {
init(initialViewState: State, imageProvider: ImageProviderProtocol? = nil) {
context = Context(initialViewState: initialViewState, imageProvider: imageProvider)
context.viewActions
.sink { [weak self] action in
guard let self else { return }
self.process(viewAction: action)
}
.store(in: &cancellables)
context.viewModel = self
}
/// Override to handles incoming `ViewAction`s from the `ViewModel`.
@ -99,4 +48,48 @@ class StateStoreViewModel<State: BindableState, ViewAction> {
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 imageProvider: ImageProviderProtocol?
/// 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, imageProvider: ImageProviderProtocol?) {
self.viewState = initialViewState
self.imageProvider = imageProvider
}
}
}

4
UnitTests/Sources/Extensions/ViewModelContext.swift
View File

@ -16,9 +16,9 @@
@testable import ElementX
extension ViewModelContext {
extension StateStoreViewModel.Context {
@discardableResult
func nextViewState() async -> ViewState? {
func nextViewState() async -> State? {
await $viewState.nextValue
}
}