ExpandGroup implementation

Sources/UIPreview/UICatalog/ExpandGroup.swift

@@ -0,0 +1,109 @@
+//
+//  SwiftUIView.swift
+//  
+//
+//  Created by Alexandr Goncharov on 28.10.2020.
+//
+
+import SwiftUI
+
+@available(iOS 14, *)
+struct ExpandGroup<Caption, Content>: View where Content: View, Caption: View {
+  @State private var defaultIsExpanded: Bool = false
+  private var isExpanded: Binding<Bool>?
+
+  var label: () -> Caption
+  var content: () -> Content
+
+  init(isExpanded: Binding<Bool>,
+       content: @escaping () -> Content,
+       label: @escaping () -> Caption) {
+    self.init(isExpanded: .some(isExpanded), content: content, label: label)
+  }
+
+  init<S>(_ caption: S,
+          isExpanded: Binding<Bool>,
+          content: @escaping () -> Content)
+  where S: StringProtocol, Caption == Text {
+    self.init(isExpanded: .some(isExpanded), content: content, label: { Text(caption) })
+  }
+
+  init(content: @escaping () -> Content,
+       label: @escaping () -> Caption) {
+    self.init(isExpanded: nil, content: content, label: label)
+  }
+
+  init<S>(_ caption: S,
+          content: @escaping () -> Content)
+  where S: StringProtocol, Caption == Text {
+    self.init(isExpanded: nil, content: content, label: { Text(caption) })
+  }
+
+  private init(isExpanded: Binding<Bool>?,
+               content: @escaping () -> Content,
+               label: @escaping () -> Caption) {
+    self.isExpanded = isExpanded
+    self.content = content
+    self.label = label
+  }
+
+  var body: some View {
+    ExpandGroupImp(
+      isExpanded: isExpanded ?? $defaultIsExpanded,
+      label: label,
+      content: content
+    )
+  }
+}
+
+@available(iOS 14, *)
+private struct ExpandGroupImp<Caption, Content>: View where Content: View, Caption: View {
+  @Binding var isExpanded: Bool
+
+  var label: () -> Caption
+  var content: () -> Content
+
+  private var chevronImage: some View {
+    Image(systemName: isExpanded
+            ? "chevron.up"
+            : "chevron.down")
+  }
+
+  @ViewBuilder
+  var body: some View {
+    VStack(alignment: .leading) {
+      Button(action: {
+        isExpanded.toggle()
+      }, label: {
+        Label(
+          title: { label() },
+          icon: { chevronImage }
+        )
+          .foregroundColor(.primary)
+      })
+      if isExpanded {
+        content()
+          .padding(.top, /*@START_MENU_TOKEN@*/10/*@END_MENU_TOKEN@*/)
+      }
+    }
+    .frame(maxWidth: .infinity)
+    .padding()
+    .background(Color(.systemGroupedBackground))
+    .cornerRadius(6)
+    .padding()
+  }
+}
+
+@available(iOS 14, *)
+struct ExpandGroup_Previews: PreviewProvider {
+  static var previews: some View {
+    ScrollView(/*@START_MENU_TOKEN@*/.vertical/*@END_MENU_TOKEN@*/) {
+      ExpandGroup() {
+        Text("Content")
+      } label: {
+        Text("Caption")
+      }
+      Spacer()
+    }
+  }
+}