Create DiffableSectionSnapshot

Author: bmarkowitz

Sources/DiffableSectionSnapshot.swift

@@ -0,0 +1,42 @@
+//
+//  Created by Jesse Squires
+//  https://www.jessesquires.com
+//
+//  Documentation
+//  https://jessesquires.github.io/ReactiveCollectionsKit
+//
+//  GitHub
+//  https://github.com/jessesquires/ReactiveCollectionsKit
+//
+//  Copyright © 2019-present Jesse Squires
+//
+
+import Foundation
+import UIKit
+
+typealias DiffableSectionSnapshot = NSDiffableDataSourceSectionSnapshot<AnyHashable>
+
+extension DiffableSectionSnapshot {
+    init(viewModel: SectionViewModel) {
+        self.init()
+
+        let allCellIdentifiers = viewModel.cells.map(\.id)
+        self.append(allCellIdentifiers)
+
+        viewModel.cells.forEach { cell in
+            appendAllChildren(from: cell, to: cell.id)
+        }
+    }
+
+    private mutating func appendAllChildren(from cell: AnyCellViewModel, to parentId: AnyHashable) {
+        let childIdentifiers = cell.children.map(\.id)
+
+        guard childIdentifiers.isNotEmpty else { return }
+
+        self.append(childIdentifiers, to: parentId)
+
+        for child in cell.children {
+            appendAllChildren(from: child, to: child.id)
+        }
+    }
+}