Add pull to refresh for Subscriptions, Popular and Trending (fixes #31)

Vendor/RefreshControl/Extensions/UIResponder+Extensions.swift

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+//
+//  UIResponder+Extensions.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 21/09/2021.
+//
+
+import Foundation
+import UIKit
+
+extension UIResponder {
+    var parentViewController: UIViewController? {
+        next as? UIViewController ?? next?.parentViewController
+    }
+}

Vendor/RefreshControl/Extensions/UIView+Extensions.swift

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+//
+//  UIView+Extensions.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 19/09/2021.
+//
+
+import Foundation
+import UIKit
+
+extension UIView {
+    /// Returs frame in screen coordinates.
+    var globalFrame: CGRect {
+        if let window = window {
+            return convert(bounds, to: window.screen.coordinateSpace)
+        } else {
+            return .zero
+        }
+    }
+
+    /// Returns with all the instances of the given view type in the view hierarchy.
+    func viewsInHierarchy<ViewType: UIView>() -> [ViewType]? {
+        var views: [ViewType] = []
+        viewsInHierarchy(views: &views)
+        return views.isEmpty ? nil : views
+    }
+
+    private func viewsInHierarchy<ViewType: UIView>(views: inout [ViewType]) {
+        subviews.forEach { eachSubView in
+            if let matchingView = eachSubView as? ViewType {
+                views.append(matchingView)
+            }
+            eachSubView.viewsInHierarchy(views: &views)
+        }
+    }
+
+    /// Search ancestral view hierarcy for the given view type.
+    func searchViewAnchestorsFor<ViewType: UIView>(
+        _ onViewFound: (ViewType) -> Void
+    ) {
+        if let matchingView = superview as? ViewType {
+            onViewFound(matchingView)
+        } else {
+            superview?.searchViewAnchestorsFor(onViewFound)
+        }
+    }
+
+    /// Search ancestral view hierarcy for the given view type.
+    func searchViewAnchestorsFor<ViewType: UIView>() -> ViewType? {
+        if let matchingView = superview as? ViewType {
+            return matchingView
+        } else {
+            return superview?.searchViewAnchestorsFor()
+        }
+    }
+
+    func printViewHierarchyInformation(_ level: Int = 0) {
+        printViewInformation(level)
+        subviews.forEach { $0.printViewHierarchyInformation(level + 1) }
+    }
+
+    func printViewInformation(_ level: Int) {
+        let leadingWhitespace = String(repeating: "    ", count: level)
+        let className = "\(Self.self)"
+        let superclassName = "\(superclass!)"
+        let frame = "\(self.frame)"
+        let id = (accessibilityIdentifier == nil) ? "" : " `\(accessibilityIdentifier!)`"
+        print("\(leadingWhitespace)\(className): \(superclassName)\(id) \(frame)")
+    }
+}

Vendor/RefreshControl/README

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+https://github.com/Geri-Borbas/iOS.Blog.SwiftUI_Pull_to_Refresh
+
+# SwiftUI Pull to Refresh
+⇣ SwiftUI Pull to Refresh (for iOS 13 and iOS 14) condensed into a single modifier.
+
+
+Complementary repository for article [**SwiftUI Pull to Refresh**] (in progress). See [`ContentView.swift`] for usage, and [`RefreshControlModifier.swift`] for the source. Designed to work with **multiple scroll views** on the same screen.
+
+```Swift
+struct ContentView: View {
+
+    var body: some View {
+        VStack {
+            HStack {
+                List {
+                    ForEach(1...100, id: \.self) { eachRowIndex in
+                        Text("Left \(eachRowIndex)")
+                    }
+                }
+                .refreshControl { refreshControl in
+                    Network.refresh {
+                        refreshControl.endRefreshing()
+                    }
+                }
+                List {
+                    ForEach(1...100, id: \.self) { eachRowIndex in
+                        Text("Right \(eachRowIndex)")
+                    }
+                }
+                .refreshControl { refreshControl in
+                    Network.refresh {
+                        refreshControl.endRefreshing()
+                    }
+                }
+            }
+        }
+    }
+}
+```
+
+
+## License
+
+> Licensed under the [**MIT License**](https://en.wikipedia.org/wiki/MIT_License).
+
+[`ContentView.swift`]: SwiftUI_Pull_to_Refresh/Views/ContentView.swift
+[`RefreshControl.swift`]: SwiftUI_Pull_to_Refresh/Views/RefreshControl.swift

Vendor/RefreshControl/RefreshControl.swift

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+//
+//  RefreshControl.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 18/09/2021.
+//
+
+import Combine
+import Foundation
+import SwiftUI
+import UIKit
+
+final class RefreshControl: ObservableObject {
+    static var navigationBarTitleDisplayMode: NavigationBarItem.TitleDisplayMode {
+        if #available(iOS 15.0, *) {
+            return .automatic
+        }
+
+        return .inline
+    }
+
+    let onValueChanged: (_ refreshControl: UIRefreshControl) -> Void
+
+    internal init(onValueChanged: @escaping ((UIRefreshControl) -> Void)) {
+        self.onValueChanged = onValueChanged
+    }
+
+    /// Adds a `UIRefreshControl` to the `UIScrollView` provided.
+    func add(to scrollView: UIScrollView) {
+        scrollView.refreshControl = UIRefreshControl().withTarget(
+            self,
+            action: #selector(onValueChangedAction),
+            for: .valueChanged
+        )
+        .testable(as: "RefreshControl")
+    }
+
+    @objc private func onValueChangedAction(sender: UIRefreshControl) {
+        onValueChanged(sender)
+    }
+}
+
+extension UIRefreshControl {
+    /// Convinience method to assign target action inline.
+    func withTarget(_ target: Any?, action: Selector, for controlEvents: UIControl.Event) -> UIRefreshControl {
+        addTarget(target, action: action, for: controlEvents)
+        return self
+    }
+
+    /// Convinience method to match refresh control for UI testing.
+    func testable(as id: String) -> UIRefreshControl {
+        isAccessibilityElement = true
+        accessibilityIdentifier = id
+        return self
+    }
+}

Vendor/RefreshControl/RefreshControlModifier.swift

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+//
+//  RefreshControlModifier.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 18/09/2021.
+//
+
+import Foundation
+import SwiftUI
+
+struct RefreshControlModifier: ViewModifier {
+    @State private var geometryReaderFrame: CGRect = .zero
+    let refreshControl: RefreshControl
+
+    internal init(onValueChanged: @escaping (UIRefreshControl) -> Void) {
+        refreshControl = RefreshControl(onValueChanged: onValueChanged)
+    }
+
+    func body(content: Content) -> some View {
+        content
+            .background(
+                GeometryReader { geometry in
+                    ScrollViewMatcher(
+                        onResolve: { scrollView in
+                            refreshControl.add(to: scrollView)
+                        },
+                        geometryReaderFrame: $geometryReaderFrame
+                    )
+                    .preference(key: FramePreferenceKey.self, value: geometry.frame(in: .global))
+                    .onPreferenceChange(FramePreferenceKey.self) { frame in
+                        self.geometryReaderFrame = frame
+                    }
+                }
+            )
+    }
+}
+
+extension View {
+    func refreshControl(onValueChanged: @escaping (_ refreshControl: UIRefreshControl) -> Void) -> some View {
+        modifier(RefreshControlModifier(onValueChanged: onValueChanged))
+    }
+}

Vendor/RefreshControl/ScrollViewMatcher/FramePreferenceKey.swift

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+//
+//  FramePreferenceKey.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 21/09/2021.
+//
+
+import Foundation
+import SwiftUI
+
+struct FramePreferenceKey: PreferenceKey {
+    typealias Value = CGRect
+    static var defaultValue = CGRect.zero
+
+    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
+        value = nextValue()
+    }
+}

Vendor/RefreshControl/ScrollViewMatcher/ScrollViewMatcher.swift

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+//
+//  ScrollViewMatcher.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 17/09/2021.
+//
+
+import Foundation
+import SwiftUI
+
+final class ScrollViewMatcher: UIViewControllerRepresentable {
+    let onMatch: (UIScrollView) -> Void
+    @Binding var geometryReaderFrame: CGRect
+
+    init(onResolve: @escaping (UIScrollView) -> Void, geometryReaderFrame: Binding<CGRect>) {
+        onMatch = onResolve
+        _geometryReaderFrame = geometryReaderFrame
+    }
+
+    func makeUIViewController(context _: Context) -> ScrollViewMatcherViewController {
+        ScrollViewMatcherViewController(onResolve: onMatch, geometryReaderFrame: geometryReaderFrame)
+    }
+
+    func updateUIViewController(_ viewController: ScrollViewMatcherViewController, context _: Context) {
+        viewController.geometryReaderFrame = geometryReaderFrame
+    }
+}
+
+final class ScrollViewMatcherViewController: UIViewController {
+    let onMatch: (UIScrollView) -> Void
+    private var scrollView: UIScrollView? {
+        didSet {
+            if oldValue != scrollView,
+               let scrollView = scrollView
+            {
+                onMatch(scrollView)
+            }
+        }
+    }
+
+    var geometryReaderFrame: CGRect {
+        didSet {
+            match()
+        }
+    }
+
+    init(onResolve: @escaping (UIScrollView) -> Void, geometryReaderFrame: CGRect, debug _: Bool = false) {
+        onMatch = onResolve
+        self.geometryReaderFrame = geometryReaderFrame
+        super.init(nibName: nil, bundle: nil)
+    }
+
+    @available(*, unavailable)
+    required init?(coder _: NSCoder) {
+        fatalError("Use init(onMatch:) to instantiate ScrollViewMatcherViewController.")
+    }
+
+    func match() {
+        // matchUsingHierarchy()
+        matchUsingGeometry()
+    }
+
+    func matchUsingHierarchy() {
+        if parent != nil {
+            // Lookup view ancestry for any `UIScrollView`.
+            view.searchViewAnchestorsFor { (scrollView: UIScrollView) in
+                self.scrollView = scrollView
+            }
+        }
+    }
+
+    func matchUsingGeometry() {
+        if let parent = parent {
+            if let scrollViewsInHierarchy: [UIScrollView] = parent.view.viewsInHierarchy() {
+                // Return first match if only a single scroll view is found in the hierarchy.
+                if scrollViewsInHierarchy.count == 1,
+                   let firstScrollViewInHierarchy = scrollViewsInHierarchy.first
+                {
+                    scrollView = firstScrollViewInHierarchy
+
+                    // Filter by frame origins if multiple matches found.
+                } else {
+                    if let firstMatchingFrameOrigin = scrollViewsInHierarchy.filter({
+                        $0.globalFrame.origin.close(to: geometryReaderFrame.origin)
+                    }).first {
+                        scrollView = firstMatchingFrameOrigin
+                    }
+                }
+            }
+        }
+    }
+
+    override func didMove(toParent parent: UIViewController?) {
+        super.didMove(toParent: parent)
+        match()
+    }
+}
+
+extension CGPoint {
+    /// Returns `true` if this point is close the other point (considering a ~1 pt tolerance).
+    func close(to point: CGPoint) -> Bool {
+        let inset = Double(1)
+        let rect = CGRect(x: x - inset, y: y - inset, width: inset * 2, height: inset * 2)
+        return rect.contains(point)
+    }
+}