oh hell ya

Author: Kyle Van Essen

BlueprintUILists/Sources/Element+HeaderFooter.swift

@@ -40,6 +40,14 @@ extension Element {
             configure: configure
         )
     }
+    
+    /// Used by internal Listable methods to  convert type-erased `Element` instances into `Item` instances.
+    func toHeaderFooterConvertible() -> AnyHeaderFooterConvertible {
+        /// We use `type(of:)` to ensure we get the actual type, not just `Element`.
+        WrappedHeaderFooterContent(
+            represented: self
+        )
+    }
 }
 
 

BlueprintUILists/Sources/List.swift

@@ -59,7 +59,7 @@ public struct List : Element
     //
     // MARK: Initialization
     //
-        
+    
     /// Create a new list, configured with the provided properties,
     /// configured with the provided `ListProperties` builder.
     public init(
@@ -76,13 +76,26 @@ public struct List : Element
     public init(
         measurement : List.Measurement = .fillParent,
         configure : ListProperties.Configure = { _ in },
-        @ListableBuilder<Section> sections : () -> [Section]
+        @ListableBuilder<Section> sections : () -> [Section],
+        @ListableOptionalBuilder<AnyHeaderFooterConvertible> containerHeader : () -> AnyHeaderFooterConvertible? = { nil },
+        @ListableOptionalBuilder<AnyHeaderFooterConvertible> header : () -> AnyHeaderFooterConvertible? = { nil },
+        @ListableOptionalBuilder<AnyHeaderFooterConvertible> footer : () -> AnyHeaderFooterConvertible? = { nil },
+        @ListableOptionalBuilder<AnyHeaderFooterConvertible> overscrollFooter : () -> AnyHeaderFooterConvertible? = { nil }
     ) {
         self.measurement = measurement
 
-        self.properties = .default(with: configure)
+        var properties = ListProperties.default {
+            $0.sections = sections()
+            
+            $0.content.containerHeader = containerHeader()
+            $0.content.header = header()
+            $0.content.footer = footer()
+            $0.content.overscrollFooter = overscrollFooter()
+        }
+        
+        configure(&properties)
 
-        self.properties.sections += sections()
+        self.properties = properties
     }
 
     //

BlueprintUILists/Sources/ListableBuilder+Element.swift

@@ -72,3 +72,28 @@ public extension ListableBuilder where ContentType == AnyItemConvertible {
     }
 }
 
+
+public extension ListableOptionalBuilder where ContentType == AnyHeaderFooterConvertible {
+
+
+    /// Enables support for `if` statements that do not have an `else`.
+    @_disfavoredOverload static func buildOptional(_ component: Element?) -> Component {
+        component?.toHeaderFooterConvertible()
+    }
+
+    /// With buildEither(second:), enables support for 'if-else' and 'switch' statements by folding conditional results into a single result.
+    @_disfavoredOverload static func buildEither(first component: Element) -> Component {
+        component.toHeaderFooterConvertible()
+    }
+
+    /// With buildEither(first:), enables support for 'if-else' and 'switch' statements by folding conditional results into a single result.
+    @_disfavoredOverload static func buildEither(second component: Element) -> Component {
+        component.toHeaderFooterConvertible()
+    }
+
+    /// If declared, this will be called on the partial result of an `if #available` block to allow the result builder to erase type information.
+    @_disfavoredOverload static func buildLimitedAvailability(_ component: Element) -> Component {
+        component.toHeaderFooterConvertible()
+    }
+}
+

ListableUI/Sources/HeaderFooter/HeaderFooter.swift

@@ -12,7 +12,7 @@ public typealias Header<Content:HeaderFooterContent> = HeaderFooter<Content>
 public typealias Footer<Content:HeaderFooterContent> = HeaderFooter<Content>
 
 
-public struct HeaderFooter<Content:HeaderFooterContent> : AnyHeaderFooter
+public struct HeaderFooter<Content:HeaderFooterContent> : AnyHeaderFooter, AnyHeaderFooterConvertible
 {
     public var content : Content
 

ListableUI/Sources/HeaderFooter/HeaderFooterContent.swift

@@ -182,6 +182,8 @@ public extension HeaderFooterContent {
     func asAnyHeaderFooter() -> AnyHeaderFooter {
         HeaderFooter(self)
     }
+    
+    
 }
 
 

ListableUI/Sources/ListableBuilder.swift

@@ -86,3 +86,52 @@
         component
     }
 }
+
+
+///
+/// A result builder which can be used to provide a SwiftUI-like DSL for building a single item.
+///
+/// You provide a result builder in an API by specifying it as a method parameter, like so:
+///
+/// ```
+/// init(@ListableBuilder<SomeContent> thing : () -> SomeContent) {
+///     self.thing = thing()
+/// }
+/// ```
+///
+/// ## Links & Videos
+/// https://github.com/apple/swift-evolution/blob/main/proposals/0289-result-builders.md
+/// https://developer.apple.com/videos/play/wwdc2021/10253/
+/// https://www.swiftbysundell.com/articles/deep-dive-into-swift-function-builders/
+/// https://www.avanderlee.com/swift/result-builders/
+///
+@resultBuilder public enum ListableOptionalBuilder<ContentType> {
+
+    /// The final value from the builder.
+    public typealias Component = ContentType?
+    
+    /// If an empty closure is provided, returns an empty array.
+    public static func buildBlock() -> Component {
+        nil
+    }
+
+    /// Enables support for `if` statements that do not have an `else`.
+    public static func buildOptional(_ component: Component?) -> Component {
+        component ?? nil
+    }
+
+    /// With buildEither(second:), enables support for 'if-else' and 'switch' statements by folding conditional results into a single result.
+    public static func buildEither(first component: Component) -> Component {
+        component
+    }
+
+    /// With buildEither(first:), enables support for 'if-else' and 'switch' statements by folding conditional results into a single result.
+    public static func buildEither(second component: Component) -> Component {
+        component
+    }
+
+    /// If declared, this will be called on the partial result of an `if #available` block to allow the result builder to erase type information.
+    public static func buildLimitedAvailability(_ component: Component) -> Component {
+        component
+    }
+}