Support backward deployment on iOS 12 with CocoaPods and Carthage

Package.swift

@@ -25,8 +25,7 @@ let package = Package(
         .target(
             name: "SDWebImageSwiftUI",
             dependencies: ["SDWebImage"],
-            path: "SDWebImageSwiftUI/Classes",
-            exclude: ["ObjC"]
+            path: "SDWebImageSwiftUI/Classes"
         ),
     ]
 )

README.md

@@ -213,7 +213,7 @@ For more information, it's really recommended to check our demo, to learn detail
 
 ### Common Problems
 
-+ Using Image/WebImage/AnimatedImage in Button/NavigationLink
+#### Using Image/WebImage/AnimatedImage in Button/NavigationLink
 
 SwiftUI's `Button` apply overlay to its content (except `Text`) by default, this is common mistake to write code like this, which cause strange behavior:
 
@@ -251,6 +251,65 @@ NavigationView {
 }
 ```
 
+#### Use for backward deployment and weak linking SwiftUI
+
+SDWebImageSwiftUI supports to use when your App Target has a deployment target version less than iOS 13/macOS 10.15/tvOS 13/watchOS 6. Which will weak linking of SwiftUI(Combine) to allows writing code with available check at runtime.
+
+To use backward deployment, you have to do the follow things:
+
++ Add `-weak_framework SwiftUI -weak_framework Combine` in your App Target's `Other Linker Flags` build setting
+
+You should notice that all the third party SwiftUI framework should have this build setting as well, not only just ourself (we already added). Or when running on iOS 12 device, it will trigger the runtime dyld error on startup.
+
++ Use CocoaPods or Carthage (SwiftPM does not support weak linking nor backward deployment currently)
+
+For Carthage user, the built binary framework will use [Library Evolution](https://swift.org/blog/abi-stability-and-more/) to support for backward deployment.
+
+For CocoaPods user, you should skip the platform validation in Podfile with
+
+```ruby
+platform :ios, '13.0' # This does not effect your App Target's deployment target version, just a hint for CocoaPods
+```
+
++ Add **all the SwiftUI code** with the available annotation and runtime check, like this:
+
+```swift
+// AppDelegate.swift
+func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
+    // ...
+    if #available(iOS 13, *) {
+        window.rootViewController = UIHostingController(rootView: contentView)
+    } else {
+        window.rootViewController = ViewController()
+    }
+    // ...
+}
+
+// ViewController.swift
+class ViewController: UIViewController {
+    var label: UILabel = UILabel()
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        self.view.backgroundColor = .white
+        self.view.addSubview(label)
+        self.label.text = "Hello World iOS 12!"
+        self.label.sizeToFit()
+        self.label.center = self.view.center
+    }
+}
+
+// ContentView.swift
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
+struct ContentView : View {
+    var body: some View {
+        Group {
+            Text("Hello World iOS 13!")
+            WebImage(url: URL(string: "https://i.loli.net/2019/09/24/rX2RkVWeGKIuJvc.jpg"))
+        }
+    }
+}
+```
+
 ## Demo
 
 To run the example using SwiftUI, following the steps:

SDWebImageSwiftUI.podspec

@@ -27,8 +27,13 @@ It brings all your favorite features from SDWebImage, like async image loading,
   s.watchos.deployment_target = '6.0'
 
   s.source_files = 'SDWebImageSwiftUI/Classes/**/*', 'SDWebImageSwiftUI/Module/*.h'
+  s.pod_target_xcconfig = {
+    'SUPPORTS_MACCATALYST' => 'YES',
+    'DERIVE_MACCATALYST_PRODUCT_BUNDLE_IDENTIFIER' => 'NO',
+    'BUILD_LIBRARY_FOR_DISTRIBUTION' => 'YES'
+  }
 
-  s.frameworks = 'SwiftUI'
+  s.weak_frameworks = 'SwiftUI', 'Combine'
   s.dependency 'SDWebImage', '~> 5.3'
   s.swift_version = '5.1'
 end

SDWebImageSwiftUI.xcodeproj/project.pbxproj

@@ -500,6 +500,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
+				BUILD_LIBRARY_FOR_DISTRIBUTION = YES;
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
@@ -552,6 +553,12 @@
 				MTL_ENABLE_DEBUG_INFO = INCLUDE_SOURCE;
 				MTL_FAST_MATH = YES;
 				ONLY_ACTIVE_ARCH = YES;
+				OTHER_LDFLAGS = (
+					"-weak_framework",
+					SwiftUI,
+					"-weak_framework",
+					Combine,
+				);
 				SDKROOT = iphoneos;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
@@ -566,6 +573,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
+				BUILD_LIBRARY_FOR_DISTRIBUTION = YES;
 				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
@@ -611,6 +619,12 @@
 				MACOSX_DEPLOYMENT_TARGET = 10.15;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				MTL_FAST_MATH = YES;
+				OTHER_LDFLAGS = (
+					"-weak_framework",
+					SwiftUI,
+					"-weak_framework",
+					Combine,
+				);
 				SDKROOT = iphoneos;
 				SWIFT_COMPILATION_MODE = wholemodule;
 				SWIFT_OPTIMIZATION_LEVEL = "-O";

SDWebImageSwiftUI/Classes/AnimatedImage.swift

@@ -12,6 +12,7 @@ import SDWebImage
 #if os(iOS) || os(tvOS) || os(macOS)
 
 /// A coordinator object used for `AnimatedImage`native view  bridge for UIKit/AppKit/WatchKit.
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public final class AnimatedImageCoordinator: NSObject {
 
     /// Any user-provided object for actual coordinator, such as delegate method, taget-action
@@ -22,6 +23,7 @@ public final class AnimatedImageCoordinator: NSObject {
 }
 
 /// Data Binding Object, only properties in this object can support changes from user with @State and refresh
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 final class AnimatedImageModel : ObservableObject {
     /// URL image
     @Published var url: URL?
@@ -36,6 +38,7 @@ final class AnimatedImageModel : ObservableObject {
 }
 
 /// Completion Handler Binding Object, supports dynamic @State changes
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 final class AnimatedImageHandler: ObservableObject {
     // Completion Handler
     @Published var successBlock: ((PlatformImage, SDImageCacheType) -> Void)?
@@ -47,6 +50,7 @@ final class AnimatedImageHandler: ObservableObject {
 }
 
 /// Layout Binding Object, supports dynamic @State changes
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 final class AnimatedImageLayout : ObservableObject {
     var contentMode: ContentMode?
     var aspectRatio: CGFloat?
@@ -58,6 +62,7 @@ final class AnimatedImageLayout : ObservableObject {
 }
 
 /// Configuration Binding Object, supports dynamic @State changes
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 final class AnimatedImageConfiguration: ObservableObject {
     var incrementalLoad: Bool?
     var maxBufferSize: UInt?
@@ -73,6 +78,7 @@ final class AnimatedImageConfiguration: ObservableObject {
 }
 
 /// A Image View type to load image from url, data or bundle. Supports animated and static image format.
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public struct AnimatedImage : PlatformViewRepresentable {
     @ObservedObject var imageModel = AnimatedImageModel()
     @ObservedObject var imageHandler = AnimatedImageHandler()
@@ -444,6 +450,7 @@ public struct AnimatedImage : PlatformViewRepresentable {
 }
 
 // Layout
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
 
     /// Configurate this view's image with the specified cap insets and options.
@@ -483,6 +490,7 @@ extension AnimatedImage {
 }
 
 // Aspect Ratio
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
     /// Constrains this view's dimensions to the specified aspect ratio.
     /// - Parameters:
@@ -541,6 +549,7 @@ extension AnimatedImage {
 }
 
 // AnimatedImage Modifier
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
 
     /// Total loop count for animated image rendering. Defaults to nil.
@@ -610,6 +619,7 @@ extension AnimatedImage {
 }
 
 // Completion Handler
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
 
     /// Provide the action when image load fails.
@@ -641,6 +651,7 @@ extension AnimatedImage {
 }
 
 // View Coordinator Handler
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
 
     /// Provide the action when view representable create the native view.
@@ -668,6 +679,7 @@ extension AnimatedImage {
 }
 
 // Web Image convenience
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension AnimatedImage {
 
     /// Associate a placeholder when loading image with url
@@ -695,6 +707,7 @@ extension AnimatedImage {
 }
 
 #if DEBUG
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 struct AnimatedImage_Previews : PreviewProvider {
     static var previews: some View {
         Group {

SDWebImageSwiftUI/Classes/ImageManager.swift

@@ -9,6 +9,7 @@
 import SwiftUI
 import SDWebImage
 
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 class ImageManager : ObservableObject {
     @Published var image: PlatformImage? // loaded image, note when progressive loading, this will published multiple times with different partial image
     @Published var isLoading: Bool = false // whether network is loading or cache is querying, should only be used for indicator binding

SDWebImageSwiftUI/Classes/ImageViewWrapper.swift

@@ -12,6 +12,7 @@ import SDWebImage
 #if os(iOS) || os(tvOS) || os(macOS)
 
 /// Use wrapper to solve tne `UIImageView`/`NSImageView` frame size become image size issue (SwiftUI's Bug)
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public class AnimatedImageViewWrapper : PlatformView {
     var wrapped = SDAnimatedImageView()
     var interpolationQuality = CGInterpolationQuality.default
@@ -67,29 +68,33 @@ public class AnimatedImageViewWrapper : PlatformView {
     }
 }
 
-private var sd_imageNameKey: Void?
-private var sd_imageDataKey: Void?
+
 /// Store the Animated Image loading state, to avoid re-query duinrg `updateView(_:)` until Source of Truth changes
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension PlatformView {
+    static private var sd_imageNameKey: Void?
+    static private var sd_imageDataKey: Void?
+
     var sd_imageName: String? {
         get {
-            objc_getAssociatedObject(self, &sd_imageNameKey) as? String
+            objc_getAssociatedObject(self, &PlatformView.sd_imageNameKey) as? String
         }
         set {
-            objc_setAssociatedObject(self, &sd_imageNameKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
+            objc_setAssociatedObject(self, &PlatformView.sd_imageNameKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
         }
     }
     var sd_imageData: Data? {
         get {
-            objc_getAssociatedObject(self, &sd_imageDataKey) as? Data
+            objc_getAssociatedObject(self, &PlatformView.sd_imageDataKey) as? Data
         }
         set {
-            objc_setAssociatedObject(self, &sd_imageDataKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
+            objc_setAssociatedObject(self, &PlatformView.sd_imageDataKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
         }
     }
 }
 
 /// Use wrapper to solve the `UIProgressView`/`NSProgressIndicator` frame origin NaN crash (SwiftUI's bug)
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public class ProgressIndicatorWrapper : PlatformView {
     #if os(macOS)
     var wrapped = NSProgressIndicator()

SDWebImageSwiftUI/Classes/Indicator/ActivityIndicator.swift

@@ -10,6 +10,7 @@ import SwiftUI
 
 #if os(macOS) || os(iOS) || os(tvOS)
 /// An activity indicator (system style)
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public struct ActivityIndicator: PlatformViewRepresentable {
     @Binding var isAnimating: Bool
     var style: Style
@@ -71,6 +72,7 @@ public struct ActivityIndicator: PlatformViewRepresentable {
     #endif
 }
 
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension ActivityIndicator {
     public enum Style {
         case medium

SDWebImageSwiftUI/Classes/Indicator/Indicator.swift

@@ -10,6 +10,7 @@ import Foundation
 import SwiftUI
 
 /// A  type to build the indicator
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public struct Indicator<T> where T : View {
     var content: (Binding<Bool>, Binding<CGFloat>) -> T
 
@@ -26,6 +27,7 @@ public struct Indicator<T> where T : View {
 /// A implementation detail View Modifier with indicator
 /// SwiftUI View Modifier construced by using a internal View type which modify the `body`
 /// It use type system to represent the view hierarchy, and Swift `some View` syntax to hide the type detail for users
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 struct IndicatorViewModifier<T> : ViewModifier where T : View {
     @ObservedObject var imageManager: ImageManager
 
@@ -44,6 +46,7 @@ struct IndicatorViewModifier<T> : ViewModifier where T : View {
 }
 
 #if os(macOS) || os(iOS) || os(tvOS)
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension Indicator where T == ActivityIndicator {
     /// Activity Indicator
     public static var activity: Indicator {
@@ -61,6 +64,7 @@ extension Indicator where T == ActivityIndicator {
     }
 }
 
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension Indicator where T == ProgressIndicator {
     /// Progress Indicator
     public static var progress: Indicator {

SDWebImageSwiftUI/Classes/Indicator/ProgressIndicator.swift

@@ -10,6 +10,7 @@ import SwiftUI
 
 #if os(macOS) || os(iOS) || os(tvOS)
 /// A progress bar indicator (system style)
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 public struct ProgressIndicator: PlatformViewRepresentable {
     @Binding var isAnimating: Bool
     @Binding var progress: CGFloat
@@ -101,6 +102,7 @@ public struct ProgressIndicator: PlatformViewRepresentable {
     #endif
 }
 
+@available(iOS 13.0, OSX 10.15, tvOS 13.0, watchOS 6.0, *)
 extension ProgressIndicator {
     public enum Style {
         case `default`