Fix no animation when popping multiple items off the path (#44)

Fixes #41 by swizzling `popToViewController(_:animated:)` and forcing
`animated: true`.

Author: davdroman

Package.swift

@@ -62,8 +62,13 @@ package.targets += [
 
     .target(name: "NavigationTransitions", dependencies: [
         "NavigationTransition",
+        "RuntimeAssociation",
+        "RuntimeSwizzling",
     ]),
 
+    .target(name: "RuntimeAssociation"),
+    .target(name: "RuntimeSwizzling"),
+
     .target(name: "TestUtils", dependencies: [
         CustomDump,
         "NavigationTransitions",

Sources/NavigationTransitions/NavigationTransition+UIKit.swift

@@ -1,4 +1,6 @@
 @_spi(package) import NavigationTransition
+import RuntimeAssociation
+import RuntimeSwizzling
 import UIKit
 
 extension AnyNavigationTransition {
@@ -115,21 +117,16 @@ extension RandomAccessCollection where Index == Int {
     }
 }
 
-extension UINavigationController {
-    private static var defaultDelegateKey = "defaultDelegate"
-    private static var customDelegateKey = "customDelegate"
-
+extension UINavigationController: RuntimeAssociation {
     private var defaultDelegate: UINavigationControllerDelegate! {
-        get { objc_getAssociatedObject(self, &Self.defaultDelegateKey) as? UINavigationControllerDelegate }
-        set { objc_setAssociatedObject(self, &Self.defaultDelegateKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
+        get { self[] }
+        set { self[] = newValue }
     }
 
     var customDelegate: NavigationTransitionDelegate! {
-        get {
-            objc_getAssociatedObject(self, &Self.customDelegateKey) as? NavigationTransitionDelegate
-        }
+        get { self[] }
         set {
-            objc_setAssociatedObject(self, &Self.customDelegateKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
+            self[] = newValue
             delegate = newValue
         }
     }
@@ -138,6 +135,13 @@ extension UINavigationController {
         _ transition: AnyNavigationTransition,
         interactivity: AnyNavigationTransition.Interactivity = .default
     ) {
+        // fix for https://stackoverflow.com/q/73753796/1922543
+        swizzle(
+            UINavigationController.self,
+            #selector(UINavigationController.popToViewController),
+            #selector(UINavigationController.popToViewController_forceAnimated)
+        )
+
         if defaultDelegate == nil {
             defaultDelegate = delegate
         }
@@ -201,42 +205,41 @@ extension UINavigationController {
     }
 }
 
+extension UINavigationController {
+    @objc func popToViewController_forceAnimated(_ viewController: UIViewController, animated: Bool) -> [UIViewController]? {
+        // TODO: `if #unavailable(iOS 17?...)` when fixed by Apple
+        popToViewController_forceAnimated(viewController, animated: true)
+    }
+}
+
 @available(tvOS, unavailable)
 extension UINavigationController {
     var defaultEdgePanRecognizer: UIScreenEdgePanGestureRecognizer! {
         interactivePopGestureRecognizer as? UIScreenEdgePanGestureRecognizer
     }
 
-    private static var defaultInteractivePanGestureRecognizer = "defaultInteractivePanGestureRecognizer"
-    private static var interactiveEdgePanGestureRecognizer = "interactiveEdgePanGestureRecognizer"
-    private static var interactivePanGestureRecognizer = "interactivePanGestureRecognizer"
-
     var defaultPanRecognizer: UIPanGestureRecognizer! {
-        get { objc_getAssociatedObject(self, &Self.defaultInteractivePanGestureRecognizer) as? UIPanGestureRecognizer }
-        set { objc_setAssociatedObject(self, &Self.defaultInteractivePanGestureRecognizer, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
+        get { self[] }
+        set { self[] = newValue }
     }
 
     var edgePanRecognizer: UIScreenEdgePanGestureRecognizer! {
-        get { objc_getAssociatedObject(self, &Self.interactiveEdgePanGestureRecognizer) as? UIScreenEdgePanGestureRecognizer }
-        set { objc_setAssociatedObject(self, &Self.interactiveEdgePanGestureRecognizer, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
+        get { self[] }
+        set { self[] = newValue }
     }
 
     var panRecognizer: UIPanGestureRecognizer! {
-        get { objc_getAssociatedObject(self, &Self.interactivePanGestureRecognizer) as? UIPanGestureRecognizer }
-        set { objc_setAssociatedObject(self, &Self.interactivePanGestureRecognizer, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
+        get { self[] }
+        set { self[] = newValue }
     }
 }
 
 @available(tvOS, unavailable)
-extension UIGestureRecognizer {
-    private static var strongDelegateKey = "strongDelegateKey"
-
+extension UIGestureRecognizer: RuntimeAssociation {
     var strongDelegate: UIGestureRecognizerDelegate? {
-        get {
-            objc_getAssociatedObject(self, &Self.strongDelegateKey) as? UIGestureRecognizerDelegate
-        }
+        get { self[] }
         set {
-            objc_setAssociatedObject(self, &Self.strongDelegateKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
+            self[] = newValue
             delegate = newValue
         }
     }

Sources/RuntimeAssociation/RuntimeAssociation.swift

@@ -0,0 +1,18 @@
+import ObjectiveC
+
+public protocol RuntimeAssociation: AnyObject {
+    subscript<T>(forKey key: String, policy: RuntimeAssociationPolicy) -> T? { get set }
+}
+
+extension RuntimeAssociation {
+    public subscript<T>(forKey key: String = #function, policy: RuntimeAssociationPolicy = .retain(.nonatomic)) -> T? {
+        get {
+            let key = unsafeBitCast(Selector(key), to: UnsafeRawPointer.self)
+            return objc_getAssociatedObject(self, key) as? T
+        }
+        set {
+            let key = unsafeBitCast(Selector(key), to: UnsafeRawPointer.self)
+            objc_setAssociatedObject(self, key, newValue, .init(policy))
+        }
+    }
+}

Sources/RuntimeAssociation/RuntimeAssociationPolicy.swift

@@ -0,0 +1,29 @@
+import ObjectiveC
+
+public enum RuntimeAssociationPolicy {
+    public enum Atomicity {
+        case atomic
+        case nonatomic
+    }
+
+    case assign
+    case copy(Atomicity)
+    case retain(Atomicity)
+}
+
+extension objc_AssociationPolicy {
+    init(_ policy: RuntimeAssociationPolicy) {
+        switch policy {
+        case .assign:
+            self = .OBJC_ASSOCIATION_ASSIGN
+        case .copy(.atomic):
+            self = .OBJC_ASSOCIATION_COPY
+        case .copy(.nonatomic):
+            self = .OBJC_ASSOCIATION_COPY_NONATOMIC
+        case .retain(.atomic):
+            self = .OBJC_ASSOCIATION_RETAIN
+        case .retain(.nonatomic):
+            self = .OBJC_ASSOCIATION_RETAIN_NONATOMIC
+        }
+    }
+}

Sources/RuntimeSwizzling/Swizzle.swift

@@ -0,0 +1,49 @@
+import ObjectiveC
+
+public var swizzleLogs = false
+
+public func swizzle(_ type: AnyObject.Type, _ original: Selector, _ swizzled: Selector) {
+    guard !swizzlingHistory.contains(type, original, swizzled) else {
+        return
+    }
+
+    swizzlingHistory.add(type, original, swizzled)
+
+    guard let originalMethod = class_getInstanceMethod(type, original) else {
+        assertionFailure("[Swizzling] Instance method \(type).\(original) not found.")
+        return
+    }
+
+    guard let swizzledMethod = class_getInstanceMethod(type, swizzled) else {
+        assertionFailure("[Swizzling] Instance method \(type).\(swizzled) not found.")
+        return
+    }
+
+    if swizzleLogs {
+        print("[Swizzling] [\(type) \(original) <~> \(swizzled)]")
+    }
+
+    method_exchangeImplementations(originalMethod, swizzledMethod)
+}
+
+fileprivate struct SwizzlingHistory {
+    private var map: [Int: Void] = [:]
+
+    func contains(_ type: AnyObject.Type, _ original: Selector, _ swizzled: Selector) -> Bool {
+        map[hash(type, original, swizzled)] != nil
+    }
+
+    mutating func add(_ type: AnyObject.Type, _ original: Selector, _ swizzled: Selector) {
+        map[hash(type, original, swizzled)] = ()
+    }
+
+    private func hash(_ type: AnyObject.Type, _ original: Selector, _ swizzled: Selector) -> Int {
+        var hasher = Hasher()
+        hasher.combine(ObjectIdentifier(type))
+        hasher.combine(original)
+        hasher.combine(swizzled)
+        return hasher.finalize()
+    }
+}
+
+fileprivate var swizzlingHistory = SwizzlingHistory()