Last active
November 24, 2022 21:40
-
-
Save paulweichhart/21f4aad6f5741c6013450acac4f4ab0e to your computer and use it in GitHub Desktop.
MVVM+SwiftUI
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// | |
// MVVM.swift | |
// MVVM+SwiftUI+Combine | |
// | |
// Created by Paul Weichhart on 07.09.20. | |
// | |
import Combine | |
import Foundation | |
import SwiftUI | |
@main | |
struct ExampleApp: App { | |
var body: some Scene { | |
WindowGroup { | |
let networkLayer = NetworkLayer() | |
let viewModel = ViewModel(networkLayer: networkLayer) | |
PortfolioView(viewModel: viewModel) | |
} | |
} | |
} | |
enum RequestError: Error { | |
case malformedURL | |
case networkError | |
} | |
struct Symbol: Codable { | |
let id: String | |
let title: String | |
var tags: String { | |
return id.localizedLowercase + " " + title.localizedLowercase | |
} | |
enum CodingKeys: String, CodingKey { | |
case id = "symbol" | |
case title | |
} | |
} | |
final class NetworkLayer { | |
private static let symbolsURL = URL(string: "https://www.paulweichhart.com/symbols.json") | |
private let decoder = JSONDecoder() | |
var symbols: AnyPublisher<[Symbol], RequestError> { | |
let publisher: AnyPublisher<[Symbol], RequestError> = fetch(url: Self.symbolsURL) | |
return publisher | |
.map { symbols in | |
return symbols.sorted(by: { $0.id < $1.id }) | |
} | |
.eraseToAnyPublisher() | |
} | |
// The generic Type `NetworkModel` allows reusing the core functionality even for Arrays | |
private func fetch<NetworkModel: Codable>(url: URL?) -> AnyPublisher<NetworkModel, RequestError> { | |
guard let url = url else { | |
// Avoid using force unwrap with returning a `RequestError` | |
return Result<NetworkModel, RequestError> | |
.Publisher(.failure(.malformedURL)) | |
.eraseToAnyPublisher() | |
} | |
return URLSession.shared.dataTaskPublisher(for: url) | |
.retry(3) | |
.map { $0.data } | |
.decode(type: NetworkModel.self, decoder: self.decoder) | |
.receive(on: RunLoop.main) | |
.mapError { _ in return .networkError } | |
.eraseToAnyPublisher() | |
} | |
} | |
final class ViewModel: ObservableObject { | |
// Using `Result` allows forwarding the Error to the View & rendering an according Error message | |
@Published private(set) var symbols: Result<[Symbol], RequestError>? | |
@Published var searchText = "" | |
private let networkLayer: NetworkLayer | |
private var cancellables = Set<AnyCancellable>() | |
init(networkLayer: NetworkLayer) { | |
self.networkLayer = networkLayer | |
subscribe() | |
} | |
private func subscribe() { | |
// SearchText has the Failure Type Never and needs to match the symbols Error Type | |
Publishers.CombineLatest(networkLayer.symbols, $searchText.setFailureType(to: RequestError.self)) | |
.map { symbols, searchText in | |
let text = searchText.localizedLowercase | |
let result = text.count < 3 ? symbols : symbols.filter { $0.tags.contains(text) } | |
return .success(result) | |
} | |
.sink(receiveCompletion: { [weak self] completion in | |
switch completion { | |
case let .failure(error): | |
self?.symbols = .failure(error) | |
case .finished: | |
break | |
} | |
}, receiveValue: { [weak self] value in | |
self?.symbols = value | |
}) | |
.store(in: &cancellables) | |
} | |
} | |
struct PortfolioView: View { | |
@StateObject private var viewModel: ViewModel | |
init(viewModel: ViewModel) { | |
_viewModel = StateObject(wrappedValue: viewModel) | |
} | |
var body: some View { | |
NavigationView { | |
VStack { | |
HeaderView(searchText: $viewModel.searchText) | |
switch viewModel.symbols { | |
case let .success(symbols): | |
PortfolioList(symbols: symbols) | |
case let .failure(error): | |
Spacer() | |
ErrorView(error: error) | |
Spacer() | |
case .none: | |
Spacer() | |
LoadingView() | |
Spacer() | |
} | |
} | |
.padding(EdgeInsets(top: 0, leading: 8.0, bottom: 0, trailing: 8.0)) | |
.navigationBarHidden(true) | |
} | |
} | |
} | |
struct HeaderView: View { | |
@Binding var searchText: String | |
var body: some View { | |
VStack(alignment: .leading) { | |
Text("Portfolio") | |
.font(.largeTitle) | |
.fontWeight(.bold) | |
.padding(EdgeInsets(top: 0, leading: 8, bottom: -8, trailing: 8)) | |
TextField("Search for Symbol", text: $searchText) | |
.padding(EdgeInsets(top: 8, leading: 8, bottom: 8, trailing: 8)) | |
.background(Color.gray.opacity(0.2)) | |
.cornerRadius(8) | |
.clipped() | |
} | |
} | |
} | |
struct LoadingView: View { | |
var body: some View { | |
VStack { | |
ProgressView() | |
Text("Loading") | |
.padding(EdgeInsets(top: 0, leading: 8.0, bottom: 0, trailing: 8.0)) | |
} | |
} | |
} | |
struct ErrorView: View { | |
let error: RequestError | |
var body: some View { | |
VStack { | |
switch error { | |
case .networkError: | |
Text("Couldn't load Symbols — please check your Internet Connection") | |
default: | |
Text("Couldn't load Symbols — please retry") | |
} | |
}.padding(EdgeInsets(top: 0, leading: 8.0, bottom: 0, trailing: 8.0)) | |
} | |
} | |
struct PortfolioList: View { | |
let symbols: [Symbol] | |
var body: some View { | |
List { | |
ForEach(symbols, id: \.id) { symbol in | |
VStack(alignment: .leading) { | |
Text(symbol.id.localizedUppercase) | |
.bold() | |
Text(symbol.title).foregroundColor(Color.gray.opacity(0.7)) | |
}.padding(EdgeInsets(top: 8, leading: 0, bottom: 8, trailing: 0)) | |
} | |
} | |
.padding(EdgeInsets(top: 0, leading: 0, bottom: 0, trailing: 16)) | |
.listStyle(PlainListStyle()) | |
} | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment