Refactory placeholder to support custom View Builder

Example/SDWebImageSwiftUIDemo/ContentView.swift

@@ -86,6 +86,9 @@ struct ContentView: View {
                             #if os(macOS) || os(iOS) || os(tvOS)
                             AnimatedImage(url: URL(string:url))
                             .indicator(SDWebImageActivityIndicator.medium)
+                            /**
+                            .placeholder(UIImage(systemName: "photo"))
+                            */
                             .transition(.fade)
                             .resizable()
                             .scaledToFit()
@@ -100,6 +103,11 @@ struct ContentView: View {
                             #if os(macOS) || os(iOS) || os(tvOS)
                             WebImage(url: URL(string:url))
                             .resizable()
+                            /**
+                             .placeholder {
+                                 Image(systemName: "photo")
+                             }
+                             */
                             .indicator(.activity)
                             .animation(.easeInOut(duration: 0.5))
                             .transition(.fade)

README.md

@@ -90,8 +90,11 @@ var body: some View {
             // Success
         }
         .resizable() // Resizable like SwiftUI.Image
+        .placeholder {
+            Image(systemName: "photo") // Placeholder
+        }
         .indicator(.activity) // Activity Indicator
-        .animation(.easeInOut(duration: 0.5))
+        .animation(.easeInOut(duration: 0.5)) // Animation Duration
         .transition(.fade) // Fade Transition
         .scaledToFit()
         .frame(width: 300, height: 300, alignment: .center)
@@ -118,6 +121,7 @@ var body: some View {
             // Error
         }
         .resizable() // Actually this is not needed unlike SwiftUI.Image
+        .placeholder(UIImage(systemName: "photo")) // Placeholder
         .indicator(SDWebImageActivityIndicator.medium) // Activity Indicator
         .transition(.fade) // Fade Transition
         .scaledToFit() // Attention to call it on AnimatedImage, but not `some View` after View Modifier

SDWebImageSwiftUI/Classes/AnimatedImage.swift

@@ -47,6 +47,7 @@ final class AnimatedImageConfiguration: ObservableObject {
     @Published var indicator: SDWebImageIndicator?
     @Published var transition: SDWebImageTransition?
     #endif
+    @Published var placeholder: PlatformImage?
 }
 
 // Convenient
@@ -67,7 +68,6 @@ public struct AnimatedImage : PlatformViewRepresentable {
     @ObservedObject var imageCoordinator = AnimatedImageCoordinator()
 
     var url: URL?
-    var placeholder: PlatformImage?
     var webOptions: SDWebImageOptions = []
     var webContext: [SDWebImageContextOption : Any]? = nil
 
@@ -80,8 +80,8 @@ public struct AnimatedImage : PlatformViewRepresentable {
     /// - Parameter placeholder: The placeholder image to show during loading
     /// - Parameter options: The options to use when downloading the image. See `SDWebImageOptions` for the possible values.
     /// - Parameter context: A context contains different options to perform specify changes or processes, see `SDWebImageContextOption`. This hold the extra objects which `options` enum can not hold.
-    public init(url: URL?, placeholder: PlatformImage? = nil, options: SDWebImageOptions = [], context: [SDWebImageContextOption : Any]? = nil) {
-        self.init(url: url, placeholder: placeholder, options: options, context: context, isAnimating: .constant(true))
+    public init(url: URL?, options: SDWebImageOptions = [], context: [SDWebImageContextOption : Any]? = nil) {
+        self.init(url: url, options: options, context: context, isAnimating: .constant(true))
     }
 
     /// Create an animated image with url, placeholder, custom options and context, including animation control binding.
@@ -90,9 +90,8 @@ public struct AnimatedImage : PlatformViewRepresentable {
     /// - Parameter options: The options to use when downloading the image. See `SDWebImageOptions` for the possible values.
     /// - Parameter context: A context contains different options to perform specify changes or processes, see `SDWebImageContextOption`. This hold the extra objects which `options` enum can not hold.
     /// - Parameter isAnimating: The binding for animation control
-    public init(url: URL?, placeholder: PlatformImage? = nil, options: SDWebImageOptions = [], context: [SDWebImageContextOption : Any]? = nil, isAnimating: Binding<Bool>) {
+    public init(url: URL?, options: SDWebImageOptions = [], context: [SDWebImageContextOption : Any]? = nil, isAnimating: Binding<Bool>) {
         self._isAnimating = isAnimating
-        self.placeholder = placeholder
         self.webOptions = options
         self.webContext = context
         self.url = url
@@ -190,7 +189,7 @@ public struct AnimatedImage : PlatformViewRepresentable {
         if currentOperation != nil {
             return
         }
-        view.wrapped.sd_setImage(with: url, placeholderImage: placeholder, options: webOptions, context: webContext, progress: { (receivedSize, expectedSize, _) in
+        view.wrapped.sd_setImage(with: url, placeholderImage: imageConfiguration.placeholder, options: webOptions, context: webContext, progress: { (receivedSize, expectedSize, _) in
             self.imageModel.progressBlock?(receivedSize, expectedSize)
         }) { (image, error, cacheType, _) in
             if let image = image {
@@ -522,12 +521,14 @@ extension AnimatedImage {
         #if os(macOS) || os(iOS) || os(tvOS)
         return self.modifier(EmptyModifier()).aspectRatio(aspectRatio, contentMode: contentMode)
         #else
-        if let aspectRatio = aspectRatio {
-            return AnyView(self.modifier(EmptyModifier()).aspectRatio(aspectRatio, contentMode: contentMode))
-        } else {
-            // on watchOS, there are no workaround like `AnimatedImageViewWrapper` to override `intrinsicContentSize`, so the aspect ratio is undetermined and cause sizing issues
-            // To workaround, we do not call default implementation for this case, using original solution instead
-            return AnyView(self)
+        return Group {
+            if aspectRatio != nil {
+                self.modifier(EmptyModifier()).aspectRatio(aspectRatio, contentMode: contentMode)
+            } else {
+                // on watchOS, there are no workaround like `AnimatedImageViewWrapper` to override `intrinsicContentSize`, so the aspect ratio is undetermined and cause sizing issues
+                // To workaround, we do not call default implementation for this case, using original solution instead
+                self
+            }
         }
         #endif
     }
@@ -650,10 +651,17 @@ extension AnimatedImage {
     }
 }
 
-#if os(macOS) || os(iOS) || os(tvOS)
 // Web Image convenience
 extension AnimatedImage {
 
+    /// Associate a placeholder when loading image with url
+    /// - Parameter content: A view that describes the placeholder.
+    public func placeholder(_ placeholder: PlatformImage?) -> AnimatedImage {
+        imageConfiguration.placeholder = placeholder
+        return self
+    }
+
+    #if os(macOS) || os(iOS) || os(tvOS)
     /// Associate a indicator when loading image with url
     /// - Note: If you do not need indicator, specify nil. Defaults to nil
     /// - Parameter indicator: indicator, see more in `SDWebImageIndicator`
@@ -669,8 +677,8 @@ extension AnimatedImage {
         imageConfiguration.transition = transition
         return self
     }
+    #endif
 }
-#endif
 
 #if DEBUG
 struct AnimatedImage_Previews : PreviewProvider {

SDWebImageSwiftUI/Classes/Indicator/Indicator.swift

@@ -11,15 +11,15 @@ import SwiftUI
 
 /// A  type to build the indicator
 public struct Indicator<T> where T : View {
-    var builder: (Binding<Bool>, Binding<CGFloat>) -> T
+    var content: (Binding<Bool>, Binding<CGFloat>) -> T
 
     /// Create a indicator with builder
     /// - Parameter builder: A builder to build indicator
     /// - Parameter isAnimating: A Binding to control the animation. If image is during loading, the value is true, else (like start loading) the value is false.
     /// - Parameter progress: A Binding to control the progress during loading. If no progress can be reported, the value is 0.
     /// Associate a indicator when loading image with url
-    public init(@ViewBuilder builder: @escaping (_ isAnimating: Binding<Bool>, _ progress: Binding<CGFloat>) -> T) {
-        self.builder = builder
+    public init(@ViewBuilder content: @escaping (_ isAnimating: Binding<Bool>, _ progress: Binding<CGFloat>) -> T) {
+        self.content = content
     }
 }
 
@@ -32,17 +32,17 @@ struct IndicatorViewModifier<T> : ViewModifier where T : View {
     var indicator: Indicator<T>
 
     func body(content: Content) -> some View {
-        if imageManager.isFinished {
-            // Disable Indiactor
-            return AnyView(content)
-        } else {
-            // Enable indicator
-            return AnyView(
+        Group {
+            if imageManager.isFinished {
+                // Disable Indiactor
+                content
+            } else {
+                // Enable indicator
                 ZStack {
                     content
-                    indicator.builder($imageManager.isLoading, $imageManager.progress)
+                    indicator.content($imageManager.isLoading, $imageManager.progress)
                 }
-            )
+            }
         }
     }
 }

SDWebImageSwiftUI/Classes/WebImage.swift

@@ -13,22 +13,23 @@ public struct WebImage : View {
     static var emptyImage = PlatformImage()
 
     var url: URL?
-    var placeholder: Image?
     var options: SDWebImageOptions
     var context: [SDWebImageContextOption : Any]?
 
     var configurations: [(Image) -> Image] = []
 
+    var placeholder: AnyView?
+    var retryOnAppear: Bool = true
+    var cancelOnDisappear: Bool = true
+
     @ObservedObject var imageManager: ImageManager
 
     /// Create a web image with url, placeholder, custom options and context.
     /// - Parameter url: The image url
-    /// - Parameter placeholder: The placeholder image to show during loading
     /// - Parameter options: The options to use when downloading the image. See `SDWebImageOptions` for the possible values.
     /// - Parameter context: A context contains different options to perform specify changes or processes, see `SDWebImageContextOption`. This hold the extra objects which `options` enum can not hold.
-    public init(url: URL?, placeholder: Image? = nil, options: SDWebImageOptions = [], context: [SDWebImageContextOption : Any]? = nil) {
+    public init(url: URL?, options: SDWebImageOptions = [], context: [SDWebImageContextOption : Any]? = nil) {
         self.url = url
-        self.placeholder = placeholder
         self.options = options
         self.context = context
         self.imageManager = ImageManager(url: url, options: options, context: context)
@@ -38,31 +39,33 @@ public struct WebImage : View {
     }
 
     public var body: some View {
-        if let platformImage = imageManager.image {
-            var image = Image(platformImage: platformImage)
-            image = configurations.reduce(image) { (previous, configuration) in
-                configuration(previous)
-            }
-            let view = image
-            return AnyView(view)
-        } else {
-            var image = placeholder ?? Image(platformImage: WebImage.emptyImage)
-            image = configurations.reduce(image) { (previous, configuration) in
-                configuration(previous)
-            }
-            let view = image
-            .onAppear {
-                if !self.imageManager.isFinished {
-                    self.imageManager.load()
+        Group {
+            if imageManager.image != nil {
+                configurations.reduce(Image(platformImage: imageManager.image!)) { (previous, configuration) in
+                    configuration(previous)
                 }
-            }
-            .onDisappear {
-                // When using prorgessive loading, the previous partial image will cause onDisappear. Filter this case
-                if self.imageManager.isLoading && !self.imageManager.isIncremental {
-                    self.imageManager.cancel()
+            } else {
+                Group {
+                    if placeholder != nil {
+                        placeholder
+                    } else {
+                        Image(platformImage: WebImage.emptyImage)
+                    }
+                }
+                .onAppear {
+                    guard self.retryOnAppear else { return }
+                    if !self.imageManager.isFinished {
+                        self.imageManager.load()
+                    }
+                }
+                .onDisappear {
+                    guard self.cancelOnDisappear else { return }
+                    // When using prorgessive loading, the previous partial image will cause onDisappear. Filter this case
+                    if self.imageManager.isLoading && !self.imageManager.isIncremental {
+                        self.imageManager.cancel()
+                    }
                 }
             }
-            return AnyView(view)
         }
     }
 }
@@ -135,6 +138,35 @@ extension WebImage {
     }
 }
 
+// WebImage Modifier
+extension WebImage {
+
+    /// Associate a placeholder when loading image with url
+    /// - note: The differences between Placeholder and Indicator, is that placeholder does not supports animation, and return type is different
+    /// - Parameter content: A view that describes the placeholder.
+    public func placeholder<T>(@ViewBuilder _ content: () -> T) -> WebImage where T : View {
+        var result = self
+        result.placeholder = AnyView(content())
+        return result
+    }
+
+    /// Control the behavior to retry the failed loading when view become appears again
+    /// - Parameter flag: Whether or not to retry the failed loading
+    public func retryOnAppear(_ flag: Bool) -> WebImage {
+        var result = self
+        result.retryOnAppear = flag
+        return result
+    }
+
+    /// Control the behavior to cancel the pending loading when view become disappear again
+    /// - Parameter flag: Whether or not to cancel the pending loading
+    public func cancelOnDisappear(_ flag: Bool) -> WebImage {
+        var result = self
+        result.cancelOnDisappear = flag
+        return result
+    }
+}
+
 // Indicator
 extension WebImage {
 
@@ -145,9 +177,9 @@ extension WebImage {
     }
 
     /// Associate a indicator when loading image with url, convenient method with block
-    /// - Parameter indicator: The indicator type, see `Indicator`
-    public func indicator<T>(@ViewBuilder builder: @escaping (_ isAnimating: Binding<Bool>, _ progress: Binding<CGFloat>) -> T) -> some View where T : View {
-        return indicator(Indicator(builder: builder))
+    /// - Parameter content: A view that describes the indicator.
+    public func indicator<T>(@ViewBuilder content: @escaping (_ isAnimating: Binding<Bool>, _ progress: Binding<CGFloat>) -> T) -> some View where T : View {
+        return indicator(Indicator(content: content))
     }
 }