一些注意事项。
您不能链接ObservableObjects，所以@ObservedObject var viewModel = BeersListViewModel() 内的class 将不起作用。
第二个你有 2 个 ViewModel 一个在 View 和一个在 Presenter 你必须选择一个。一个人不会知道另一个人在做什么。
下面是如何让你的代码工作
import SwiftUI
struct Beer: Identifiable{
var id: UUID = UUID()
var name: String = "Hops"
var abv: String = "H"
}
protocol BeersListInteractorProtocol{
func loadList(at: Int, completion: ([Beer])->Void)
}
struct BeersListInteractor: BeersListInteractorProtocol{
func loadList(at: Int, completion: ([Beer]) -> Void) {
completion([Beer(), Beer(), Beer()])
}
}
protocol BeersListPresenterProtocol: ObservableObject{
var interactor: BeersListInteractorProtocol { get set }
var viewModel : BeersListViewModel { get set }
func formattedABV(_ abv: String) -> String
func loadList(at page: Int)
}
class BeersListPresenter: BeersListPresenterProtocol, ObservableObject{
var interactor: BeersListInteractorProtocol
//You can't chain `ObservedObject`s
@Published var viewModel = BeersListViewModel()
init(interactor: BeersListInteractorProtocol){
self.interactor = interactor
}
func loadList(at page: Int){
interactor.loadList(at: page) { beers in
DispatchQueue.main.async {
self.viewModel.beers.append(contentsOf: beers)
print(self.viewModel.beers)
}
}
}
func formattedABV(_ abv: String) -> String{
"**\(abv)**"
}
}
//Change to struct
struct BeersListViewModel{
var beers = [Beer]()
}
struct BeerListView<T: BeersListPresenterProtocol>: View{
//This is what will trigger view updates
@StateObject var presenter : T
//The viewModel is in the Presenter
//@StateObject var viewModel : BeersListViewModel
var body: some View {
NavigationView{
List{
Button("load list", action: {
presenter.loadList(at: 1)
})
ForEach(presenter.viewModel.beers, id: \.id){ beer in
HStack{
VStack(alignment: .leading){
Text(beer.name)
.font(.headline)
Text("Vol: \(presenter.formattedABV(beer.abv))")
.font(.subheadline)
}
}
}
}
}
}
}
struct BeerListView_Previews: PreviewProvider {
static var previews: some View {
BeerListView(presenter: BeersListPresenter(interactor: BeersListInteractor()))
}
}
现在我无论如何都不是 VIPER 专家，但我认为你在混合概念。混合使用 MVVM 和 VIPER。因为在 VIPER 中，presenter 存在于 View/ViewModel 之下，而不是处于同一级别。
我不久前找到了this 教程。它适用于 UIKit，但如果我们使用 ObservableObject 代替 UIViewController 而 SwiftUI View 充当故事板。
它使ViewModel（即ObservableObject）和View（即SwiftUI struct）在VIPER 方面成为单个View 层。
你会得到类似这样的代码
protocol BeersListPresenterProtocol{
var interactor: BeersListInteractorProtocol { get set }
func formattedABV(_ abv: String) -> String
func loadList(at: Int, completion: ([Beer]) -> Void)
}
struct BeersListPresenter: BeersListPresenterProtocol{
var interactor: BeersListInteractorProtocol
init(interactor: BeersListInteractorProtocol){
self.interactor = interactor
}
func loadList(at: Int, completion: ([Beer]) -> Void) {
interactor.loadList(at: at) { beers in
completion(beers)
}
}
func formattedABV(_ abv: String) -> String{
"**\(abv)**"
}
}
protocol BeersListViewProtocol: ObservableObject{
var presenter: BeersListPresenterProtocol { get set }
var beers: [Beer] { get set }
func loadList(at: Int)
func formattedABV(_ abv: String) -> String
}
class BeersListViewModel: BeersListViewProtocol{
@Published var presenter: BeersListPresenterProtocol
@Published var beers: [Beer] = []
init(presenter: BeersListPresenterProtocol){
self.presenter = presenter
}
func loadList(at: Int) {
DispatchQueue.main.async {
self.presenter.loadList(at: at, completion: {beers in
self.beers = beers
})
}
}
func formattedABV(_ abv: String) -> String {
presenter.formattedABV(abv)
}
}
struct BeerListView<T: BeersListViewProtocol>: View{
@StateObject var viewModel : T
var body: some View {
NavigationView{
List{
Button("load list", action: {
viewModel.loadList(at: 1)
})
ForEach(viewModel.beers, id: \.id){ beer in
HStack{
VStack(alignment: .leading){
Text(beer.name)
.font(.headline)
Text("Vol: \(viewModel.formattedABV(beer.abv))")
.font(.subheadline)
}
}
}
}
}
}
}
struct BeerListView_Previews: PreviewProvider {
static var previews: some View {
BeerListView(viewModel: BeersListViewModel(presenter: BeersListPresenter(interactor: BeersListInteractor())))
}
}
如果您不想将 VIPER 视图层分为 ViewModel 和 SwiftUI View 您可以选择执行以下代码之类的操作，但这会使替换 UI 变得更加困难，并且通常是不是一个好习惯。因为当interactor 有更新时，您将无法从presenter 调用方法。
struct BeerListView<T: BeersListPresenterProtocol>: View, BeersListViewProtocol{
var presenter: BeersListPresenterProtocol
@State var beers: [Beer] = []
var body: some View {
NavigationView{
List{
Button("load list", action: {
loadList(at: 1)
})
ForEach(beers, id: \.id){ beer in
HStack{
VStack(alignment: .leading){
Text(beer.name)
.font(.headline)
Text("Vol: \(formattedABV(beer.abv))")
.font(.subheadline)
}
}
}
}
}
}
func loadList(at: Int) {
DispatchQueue.main.async {
self.presenter.loadList(at: at, completion: {beers in
self.beers = beers
})
}
}
func formattedABV(_ abv: String) -> String {
presenter.formattedABV(abv)
}
}
struct BeerListView_Previews: PreviewProvider {
static var previews: some View {
BeerListView<BeersListPresenter>(presenter: BeersListPresenter(interactor: BeersListInteractor()))
}
}