Tiled

.claude/settings.local.json

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+{
+  "permissions": {
+    "allow": [
+      "mcp__XcodeBuildMCP__discover_projs",
+      "mcp__sosumi__searchAppleDocumentation",
+      "WebFetch(domain:medium.com)",
+      "Bash(tee:*)"
+    ]
+  }
+}

CLAUDE.md

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+- Always build for iOS

Dev/MessagingUIDevelopment/ApplyDiffDemo.swift

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+//
+//  ApplyDiffDemo.swift
+//  MessagingUIDevelopment
+//
+//  Created by Hiroshi Kimura on 2025/12/12.
+//
+
+import SwiftUI
+import MessagingUI
+
+// MARK: - ApplyDiff Demo
+
+/// Demonstrates the `applyDiff(from:)` method which automatically detects
+/// prepend, append, insert, update, and remove operations from array differences.
+struct BookApplyDiffDemo: View {
+
+  @State private var dataSource = ListDataSource<ChatMessage>()
+
+  /// Source of truth - the "server" data
+  @State private var serverItems: [ChatMessage] = []
+
+  /// Next ID for new items
+  @State private var nextId = 0
+
+  /// Log of operations performed
+  @State private var operationLog: [String] = []
+
+  /// Previous change counter to detect new changes
+  @State private var previousChangeCounter = 0
+
+  @State private var scrollPosition = TiledScrollPosition()
+
+  var body: some View {
+    VStack(spacing: 0) {
+      // Control Panel
+      VStack(spacing: 12) {
+        Text("applyDiff Demo")
+          .font(.headline)
+
+        Text("Modify the 'server' array, then applyDiff auto-detects changes")
+          .font(.caption)
+          .foregroundStyle(.secondary)
+          .multilineTextAlignment(.center)
+
+        // Row 1: Basic operations
+        HStack {
+          Button("Prepend") {
+            let newItem = ChatMessage(id: nextId, text: "Prepended #\(nextId)")
+            nextId += 1
+            serverItems.insert(newItem, at: 0)
+            applyAndLog("prepend(1)")
+          }
+          .buttonStyle(.bordered)
+
+          Button("Append") {
+            let newItem = ChatMessage(id: nextId, text: "Appended #\(nextId)")
+            nextId += 1
+            serverItems.append(newItem)
+            applyAndLog("append(1)")
+          }
+          .buttonStyle(.bordered)
+
+          Button("Insert Mid") {
+            guard serverItems.count >= 2 else {
+              serverItems.append(ChatMessage(id: nextId, text: "First #\(nextId)"))
+              nextId += 1
+              applyAndLog("setItems")
+              return
+            }
+            let midIndex = serverItems.count / 2
+            let newItem = ChatMessage(id: nextId, text: "Inserted #\(nextId)")
+            nextId += 1
+            serverItems.insert(newItem, at: midIndex)
+            applyAndLog("insert@\(midIndex)(1)")
+          }
+          .buttonStyle(.bordered)
+        }
+
+        // Row 2: Update / Remove
+        HStack {
+          Button("Update First") {
+            guard !serverItems.isEmpty else { return }
+            serverItems[0].text = "Updated! \(Date().formatted(date: .omitted, time: .standard))"
+            applyAndLog("update(1)")
+          }
+          .buttonStyle(.bordered)
+
+          Button("Remove Last") {
+            guard !serverItems.isEmpty else { return }
+            serverItems.removeLast()
+            applyAndLog("remove(1)")
+          }
+          .buttonStyle(.bordered)
+
+          Button("Shuffle") {
+            serverItems.shuffle()
+            applyAndLog("shuffle→setItems")
+          }
+          .buttonStyle(.bordered)
+        }
+
+        // Row 3: Complex operations
+        HStack {
+          Button("Prepend+Update+Remove") {
+            guard serverItems.count >= 2 else {
+              // Initialize with some items
+              serverItems = [
+                ChatMessage(id: nextId, text: "Item A"),
+                ChatMessage(id: nextId + 1, text: "Item B"),
+                ChatMessage(id: nextId + 2, text: "Item C"),
+              ]
+              nextId += 3
+              applyAndLog("setItems(3)")
+              return
+            }
+
+            // Prepend new item
+            let newItem = ChatMessage(id: nextId, text: "New Prepended #\(nextId)")
+            nextId += 1
+            serverItems.insert(newItem, at: 0)
+
+            // Update second item (was first before prepend)
+            if serverItems.count > 1 {
+              serverItems[1].text = "Updated!"
+            }
+
+            // Remove last item
+            serverItems.removeLast()
+
+            applyAndLog("remove+prepend+update")
+          }
+          .buttonStyle(.bordered)
+          .tint(.orange)
+
+          Button("Reset") {
+            serverItems = []
+            nextId = 0
+            operationLog = []
+            previousChangeCounter = 0
+            dataSource = ListDataSource()
+          }
+          .buttonStyle(.borderedProminent)
+          .tint(.red)
+        }
+
+        // Stats
+        HStack {
+          Text("Items: \(serverItems.count)")
+          Spacer()
+          Text("ChangeCounter: \(dataSource.changeCounter)")
+        }
+        .font(.caption)
+        .foregroundStyle(.secondary)
+      }
+      .padding()
+      .background(Color(.systemBackground))
+
+      Divider()
+
+      // Operation Log
+      VStack(alignment: .leading, spacing: 4) {
+        Text("Operation Log (expected changes):")
+          .font(.caption.bold())
+        ScrollView(.horizontal, showsIndicators: false) {
+          HStack(spacing: 8) {
+            ForEach(operationLog.suffix(10), id: \.self) { log in
+              Text(log)
+                .font(.caption2)
+                .padding(.horizontal, 8)
+                .padding(.vertical, 4)
+                .background(logColor(for: log).opacity(0.2))
+                .clipShape(RoundedRectangle(cornerRadius: 4))
+            }
+          }
+        }
+      }
+      .padding(.horizontal)
+      .padding(.vertical, 8)
+      .background(Color(.secondarySystemBackground))
+
+      Divider()
+
+      // List View
+      TiledView(
+        dataSource: dataSource,
+        scrollPosition: $scrollPosition,
+        cellBuilder: { message in
+          ChatBubbleView(message: message)
+        }
+      )
+    }
+  }
+
+  private func applyAndLog(_ expectedChange: String) {
+    var updatedDataSource = dataSource
+    updatedDataSource.applyDiff(from: serverItems)
+
+    // Check if change counter increased
+    let newCounter = updatedDataSource.changeCounter
+    if newCounter > previousChangeCounter {
+      operationLog.append(expectedChange)
+      previousChangeCounter = newCounter
+    }
+
+    dataSource = updatedDataSource
+  }
+
+  private func logColor(for log: String) -> Color {
+    if log.contains("prepend") { return .blue }
+    if log.contains("append") { return .green }
+    if log.contains("insert") { return .purple }
+    if log.contains("update") { return .orange }
+    if log.contains("remove") { return .red }
+    if log.contains("setItems") || log.contains("shuffle") { return .gray }
+    return .primary
+  }
+}
+
+#Preview("ApplyDiff Demo") {
+  BookApplyDiffDemo()
+}