SwiftUI - Pull to Refresh

ContentView.swift

//
//  ContentView.swift
//  PullToRefresh
//
//  Created by Alexey Belousov on 20.03.2020.
//  Copyright © 2020 AskJack. All rights reserved.
//

import SwiftUI
import Combine

private let kFirstNames = [
    "James", "John", "Robert", "Michael", "William",
    "David", "Richard", "Joseph", "Charles", "Thomas",
]

private let kLastNames = [
    "Adams", "Allen", "Anderson", "Armstrong", "Atkinson",
    "Bailey", "Baker", "Ball", "Barker", "Barnes",
]

struct Record: Identifiable {
    
    let id: Int
    let name: String
    let amount: Int
    
}

struct Generator {
    
    static let `default` = Generator()
    
    private func randomName() -> String {
        [
            kFirstNames.randomElement(),
            kLastNames.randomElement()
        ].compactMap { $0 }
            .joined(separator: " ")
    }
    
    public func generate(_ count: Int = 10) -> AnyPublisher<[Record], Never> {
        Just((0..<count).map {
            Record(id: $0 + 1, name: randomName(), amount: Int.random(in: 50..<500))
        }).setFailureType(to: Never.self)
            .eraseToAnyPublisher()
    }
    
}

struct ContentView: View {
    
    @State private var records: [Record] = []
    
    @State private var disposables = Set<AnyCancellable>()
    
    private let generator: Generator = .default
    
    var body: some View {
        NavigationView {
            ZStack {
                ScrollViewAppearance(action: pullToRefresh) {
                    ZStack {
                        Color.red.opacity(0.05)
                            .edgesIgnoringSafeArea(.bottom)
                    
                        ScrollView {
                            VStack(spacing: 8) {
                                ForEach(records) { record in
                                    HStack {
                                        VStack(alignment: .leading, spacing: 8) {
                                            HStack {
                                                Text("#\(record.id)")
                                                Text(record.name)
                                            }.font(.headline)
                                            
                                            Text("Amount: \(record.amount)")
                                                .font(.callout)
                                        }
                                        
                                        Spacer()
                                    }.padding()
                                        .background(Color.white)
                                        .cornerRadius(10)
                                        .shadow(radius: 5)
                                }
                            }.padding()
                            
                            Divider()
                                .hidden()
                        }
                    }
                }.edgesIgnoringSafeArea(.bottom)
            }.navigationBarTitle("Pull to Refresh", displayMode: .inline)
                .onAppear(perform: fetch)
        }
    }
    
}

extension ContentView {
    
    private func fetch() {
        generator.generate()
            .receive(on: RunLoop.main)
            .assign(to: \.records, on: self)
            .store(in: &disposables)
    }
    
    private func pullToRefresh(refreshControl: UIRefreshControl) {
        print(#function)
        generator.generate()
            .receive(on: RunLoop.main)
            .sink { records in
                self.records = records
                refreshControl.endRefreshing()
            }
            .store(in: &disposables)
    }
    
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

ScrollViewAppearance.swift

//
//  ScrollViewAppearance.swift
//  PullToRefresh
//
//  Created by Alexey Belousov on 20.03.2020.
//  Copyright © 2020 AskJack. All rights reserved.
//

import SwiftUI
import Combine

struct ScrollViewAppearance<Content>: UIViewControllerRepresentable where Content: View {
    
    typealias UIViewControllerType = UIHostingController<Content>
    
    class Coordinator: NSObject {
    
        private let action: (UIRefreshControl) -> Void
        
        init(action: @escaping (UIRefreshControl) -> Void) {
            self.action = action
        }
        
        @objc func handleRefreshControl(sender: UIRefreshControl) {
            action(sender)
        }
        
    }
    
    private let action: (UIRefreshControl) -> Void
    
    private let content: Content
    
    init(action handler: @escaping (UIRefreshControl) -> Void, @ViewBuilder content builder: () -> Content) {
        action = handler
        content = builder()
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(action: action)
    }
    
    func makeUIViewController(context: Context) -> UIHostingController<Content> {
        let scrollView = UIScrollView.appearance(whenContainedInInstancesOf: [UIViewControllerType.self])
        scrollView.refreshControl = UIRefreshControl()
        scrollView.refreshControl?.addTarget(context.coordinator, action: #selector(Coordinator.handleRefreshControl(sender:)), for: .valueChanged)
        return UIHostingController(rootView: content)
    }
    
    func updateUIViewController(_ uiViewController: UIHostingController<Content>, context: Context) {
        uiViewController.rootView = content
    }
    
}