Refactory placeholder arg with a view modifier API, make it more suitable for common usage

Author: dreampiggy

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 +13,20 @@ public struct WebImage : View {
     static var emptyImage = PlatformImage()
 
     var url: URL?
-    var placeholder: Image?
     var options: SDWebImageOptions
     var context: [SDWebImageContextOption : Any]?
 
+    var placeholder: AnyView?
     var configurations: [(Image) -> Image] = []
 
     @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 +36,31 @@ 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 {
+                    if !self.imageManager.isFinished {
+                        self.imageManager.load()
+                    }
+                }
+                .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()
+                    }
                 }
             }
-            return AnyView(view)
         }
     }
 }
@@ -135,6 +133,19 @@ extension WebImage {
     }
 }
 
+// Placeholder
+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
+    }
+}
+
 // Indicator
 extension WebImage {
 
@@ -145,9 +156,9 @@ 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))
     }
 }