Implement PreviewGroup

Author: MihaelIsaev

Classes/Structs/LivePreview.swift

@@ -153,6 +153,15 @@ public class Preview {
         semanticContentAttribute = v ? .forceRightToLeft : .forceLeftToRight
         return self
     }
+    
+    fileprivate var liveView: some SwiftUI.View {
+        LiveView(view)
+            .preferredColorScheme(colorScheme.val)
+            .previewLayout(layout)
+            .previewDisplayName(title)
+            .edgesIgnoringSafeArea(.all)
+            .previewDevice(device.name == "none" ? nil : PreviewDevice(rawValue: device.name))
+    }
 }
 
 public protocol DeclarativePreview: SwiftUI.PreviewProvider {
@@ -165,12 +174,52 @@ extension DeclarativePreview {
     public static var previews: some SwiftUI.View {
         Localization.current = preview.language
         UIView.appearance().semanticContentAttribute = preview.semanticContentAttribute
-        return LiveView(preview.view)
-            .preferredColorScheme(preview.colorScheme.val)
-            .previewLayout(preview.layout)
-            .previewDisplayName(preview.title)
-            .edgesIgnoringSafeArea(.all)
-            .previewDevice(preview.device.name == "none" ? nil : PreviewDevice(rawValue: preview.device.name))
+        return preview.liveView
+    }
+}
+
+public protocol DeclarativePreviewGroup: SwiftUI.PreviewProvider {
+    @available(iOS 13.0, *)
+    static var previewGroup: PreviewGroup { get }
+}
+
+extension DeclarativePreviewGroup {
+    @available(iOS 13.0, *)
+    public static var previews: some SwiftUI.View {
+        Localization.current = previewGroup.language
+        UIView.appearance().semanticContentAttribute = previewGroup.semanticContentAttribute
+        return SwiftUI.Group {
+            if previewGroup.previews.count > 0 {
+                previewGroup.previews[0].liveView
+            }
+            if previewGroup.previews.count > 1 {
+                previewGroup.previews[1].liveView
+            }
+            if previewGroup.previews.count > 2 {
+                previewGroup.previews[2].liveView
+            }
+            if previewGroup.previews.count > 3 {
+                previewGroup.previews[3].liveView
+            }
+            if previewGroup.previews.count > 4 {
+                previewGroup.previews[4].liveView
+            }
+            if previewGroup.previews.count > 5 {
+                previewGroup.previews[5].liveView
+            }
+            if previewGroup.previews.count > 6 {
+                previewGroup.previews[6].liveView
+            }
+            if previewGroup.previews.count > 7 {
+                previewGroup.previews[7].liveView
+            }
+            if previewGroup.previews.count > 8 {
+                previewGroup.previews[8].liveView
+            }
+            if previewGroup.previews.count > 9 {
+                previewGroup.previews[9].liveView
+            }
+        }
     }
 }
 #endif

Classes/Structs/PreviewBuilder.swift

@@ -0,0 +1,66 @@
+import UIKit
+
+@available(iOS 13.0, *)
+public class PreviewGroup {
+    let previews: [Preview]
+    var language: Language = Localization().detectCurrentLanguage()
+    var semanticContentAttribute: UISemanticContentAttribute = .unspecified
+    
+    public init (@PreviewBuilder block: PreviewBuilder.Block) {
+        previews = block().previewBuilderItems
+    }
+    
+    @discardableResult
+    public func language(_ v: Language) -> Self {
+        language = v
+        return self
+    }
+    
+    @discardableResult
+    public func rtl(_ v: Bool) -> Self {
+        semanticContentAttribute = v ? .forceRightToLeft : .forceLeftToRight
+        return self
+    }
+}
+
+@available(iOS 13.0, *)
+@_functionBuilder public struct PreviewBuilder {
+    public typealias Block = () -> PreviewBuilderItem
+    
+    /// Builds an empty preview from an block containing no statements, `{ }`.
+    public static func buildBlock() -> PreviewBuilderItem { [] }
+    
+    /// Passes a single preview written as a child view (e..g, `{ Text("Hello") }`) through unmodified.
+    public static func buildBlock(_ attrs: PreviewBuilderItem...) -> PreviewBuilderItem {
+        buildBlock(attrs)
+    }
+    
+    /// Passes a single preview written as a child view (e..g, `{ Text("Hello") }`) through unmodified.
+    public static func buildBlock(_ attrs: [PreviewBuilderItem]) -> PreviewBuilderItem {
+        PreviewBuilderItems(items: attrs.flatMap { $0.previewBuilderItems })
+    }
+    
+    /// Provides support for "if" statements in multi-statement closures, producing an `Optional` preview
+    /// that is visible only when the `if` condition evaluates `true`.
+    public static func buildIf(_ content: PreviewBuilderItem?) -> PreviewBuilderItem {
+        guard let content = content else { return [] }
+        return content
+    }
+    
+    /// Provides support for "if" statements in multi-statement closures, producing
+    /// ConditionalContent for the "then" branch.
+    public static func buildEither(first: PreviewBuilderItem) -> PreviewBuilderItem {
+        first
+    }
+
+    /// Provides support for "if-else" statements in multi-statement closures, producing
+    /// ConditionalContent for the "else" branch.
+    public static func buildEither(second: PreviewBuilderItem) -> PreviewBuilderItem {
+        second
+    }
+}
+
+@available(iOS 13.0, *)
+extension Array: PreviewBuilderItem where Element: Preview {
+    public var previewBuilderItems: [Preview] { self }
+}

Classes/Structs/PreviewBuilderItem.swift

@@ -0,0 +1,22 @@
+import UIKit
+
+@available(iOS 13.0, *)
+public protocol PreviewBuilderItem {
+    var previewBuilderItems: [Preview] { get }
+}
+
+@available(iOS 13.0, *)
+public struct PreviewBuilderItems: PreviewBuilderItem {
+    public let items: [Preview]
+    
+    public init (items: [Preview]) {
+        self.items = items
+    }
+    
+    public var previewBuilderItems: [Preview] { items }
+}
+
+@available(iOS 13.0, *)
+extension Preview: PreviewBuilderItem {
+    public var previewBuilderItems: [Preview] { [self] }
+}

README.md

@@ -40,7 +40,7 @@ Good mood
 
 Add the following line to your Podfile:
 ```ruby
-pod 'UIKit-Plus', '~> 1.19.0'
+pod 'UIKit-Plus', '~> 1.20.0'
 ```
 
 #### With [Swift Package Manager](https://swift.org/package-manager/)
@@ -165,21 +165,32 @@ Live preview provided by SwiftUI (available only since macOS Catalina).
 
 > The only problem we have is that since names of views are the same in `UIKitPlus` and `SwiftUI` we should use aliases like `UButton` for `Button` or `UView` for `View`, so everything with `U` prefix. It is only necessary if you want to use live previews, otherwise there is no need to import `SwiftUI`, so no name conflicts.
 
+#### Preview single item
+
+> 💡 You can create as many preview structs as you need
+
+`ViewController` example
+
 ```swift
 #if canImport(SwiftUI)
 import SwiftUI
 @available(iOS 13.0, *)
 struct MyViewController_Preview: PreviewProvider, DeclarativePreview {
-    Preview {
-        MainViewController()
+    static var preview: Preview {
+        Preview {
+            MainViewController()
+        }
+        .colorScheme(.dark)
+        .device(.iPhoneX)
+        .language(.fr)
+        .rtl(true)
     }
-    .colorScheme(.dark)
-    .device(.iPhoneX)
-    .language(.fr)
-    .rtl(true)
 }
 #endif
 ```
+
+`View` example
+
 ```swift
 #if canImport(SwiftUI)
 import SwiftUI
@@ -204,6 +215,42 @@ struct MyButton_Preview: PreviewProvider, DeclarativePreview {
 #endif
 ```
 
+#### Preview group 🔥
+
+It is just convenience way to create multiple previews inside one struct, but it has limitations related to `rtl` and `language` properties which should be set to whole group
+
+```swift
+#if canImport(SwiftUI)
+import SwiftUI
+@available(iOS 13.0, *)
+struct MyViewController_Preview: PreviewProvider, DeclarativePreviewGroup {
+    static var previewGroup: PreviewGroup {
+        PreviewGroup { // 1 to 10 previews inside
+            Preview {
+                MainViewController()
+            }
+            .colorScheme(.dark)
+            .device(.iPhoneX)
+            Preview {
+                MainViewController()
+            }
+            .colorScheme(.light)
+            .device(.iPhoneX)
+            UButton(String(.en("Hello"), .fr("Bonjour"), .ru("Привет"))) // in this group title will be shown in `fr`
+                .circle()
+                .background(.blackHole / .white)
+                .color(.white / .black)
+                .height(54)
+                .edgesToSuperview(h: 8)
+                .centerYInSuperview()
+        }
+        .language(.fr) // limited to group
+        .rtl(true) // limited to group
+    }
+}
+#endif
+```
+
 ## Usage
 
 ```swift

UIKit-Plus.podspec

@@ -9,7 +9,7 @@
 Pod::Spec.new do |s|
   s.name               = 'UIKit-Plus'
   s.module_name   = 'UIKitPlus'
-  s.version             = '1.19.0'
+  s.version             = '1.20.0'
   s.summary          = '🏰 Declarative UIKit wrapper inspired by SwiftUI'
 
   s.swift_version    = '5.2'