add type-safe sections accessor for compositional layout (#8)

Author: JohnEstropia

Sources/DynamicList/DynamicListView.swift

@@ -137,6 +137,28 @@ public final class DynamicListView<Section: Hashable, Data: Hashable>: UIView,
 
   private let contentPagingTrigger: ContentPagingTrigger
 
+  convenience public init(
+    sectionProvider: @escaping (Section, NSCollectionLayoutEnvironment) -> NSCollectionLayoutSection,
+    contentInsetAdjustmentBehavior: UIScrollView.ContentInsetAdjustmentBehavior = .automatic
+  ) {
+    weak var weakSelf: DynamicListView?
+    self.init(
+      layout: UICollectionViewCompositionalLayout.init(
+        sectionProvider: { sectionIndex, environment in
+          guard let `self` = weakSelf else {
+            return nil
+          }
+          return sectionProvider(
+            self.snapshot().sectionIdentifiers[sectionIndex],
+            environment
+          )
+        }
+      ),
+      contentInsetAdjustmentBehavior: contentInsetAdjustmentBehavior
+    )
+    weakSelf = self
+  }
+
   public init(
     layout: UICollectionViewCompositionalLayout,
     contentInsetAdjustmentBehavior: UIScrollView.ContentInsetAdjustmentBehavior = .automatic