Merge pull request #1160 from Adlai-Holler/AHUpdateSwiftExample

[Swift] Update Swift Example, resolve build issue with some Swift projects.

AsyncDisplayKit.podspec

@@ -13,13 +13,19 @@ Pod::Spec.new do |spec|
       'AsyncDisplayKit/*.h',
       'AsyncDisplayKit/Details/**/*.h',
       'AsyncDisplayKit/Layout/*.h',
-      'AsyncDisplayKit/TextKit/*.h',
+      'Base/*.h',
-      'Base/*.h'
+      'AsyncDisplayKit/TextKit/ASTextNodeTypes.h'
   ]
 
   spec.source_files = [
       'AsyncDisplayKit/**/*.{h,m,mm}',
-      'Base/*.{h,m}'
+      'Base/*.{h,m}',
+      
+      # Most TextKit components are not public because the C++ content
+      # in the headers will cause build errors when using
+      # `use_frameworks!` on 0.39.0 & Swift 2.1.
+      # See https://github.com/facebook/AsyncDisplayKit/issues/1153
+      'AsyncDisplayKit/TextKit/*.h',
   ]
 
   spec.frameworks = 'AssetsLibrary'

examples/Kittens/Sample/ViewController.m

@@ -165,28 +165,24 @@ static const NSInteger kMaxLitterSize = 100;        // max number of kitten cell
 
 - (void)tableView:(UITableView *)tableView willBeginBatchFetchWithContext:(ASBatchContext *)context
 {
-  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
-    sleep(1);
+    // populate a new array of random-sized kittens
-    dispatch_async(dispatch_get_main_queue(), ^{
+    NSArray *moarKittens = [self createLitterWithSize:kLitterBatchSize];
-        
-      // populate a new array of random-sized kittens
-      NSArray *moarKittens = [self createLitterWithSize:kLitterBatchSize];
 
-      NSMutableArray *indexPaths = [[NSMutableArray alloc] init];
+    NSMutableArray *indexPaths = [[NSMutableArray alloc] init];
-        
+      
-      // find number of kittens in the data source and create their indexPaths
+    // find number of kittens in the data source and create their indexPaths
-      NSInteger existingRows = _kittenDataSource.count + 1;
+    NSInteger existingRows = _kittenDataSource.count + 1;
-        
+      
-      for (NSInteger i = 0; i < moarKittens.count; i++) {
+    for (NSInteger i = 0; i < moarKittens.count; i++) {
-        [indexPaths addObject:[NSIndexPath indexPathForRow:existingRows + i inSection:0]];
+      [indexPaths addObject:[NSIndexPath indexPathForRow:existingRows + i inSection:0]];
-      }
+    }
 
-      // add new kittens to the data source & notify table of new indexpaths
+    // add new kittens to the data source & notify table of new indexpaths
-      [_kittenDataSource addObjectsFromArray:moarKittens];
+    [_kittenDataSource addObjectsFromArray:moarKittens];
-      [tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];
+    [tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];
 
-      [context completeBatchFetching:YES];
+    [context completeBatchFetching:YES];
-    });
   });
 }
 

examples/Swift/Podfile

@@ -1,3 +1,6 @@
 source 'https://github.com/CocoaPods/Specs.git'
 platform :ios, '8.0'
+
+use_frameworks!
+
 pod 'AsyncDisplayKit', :path => '../..'

examples/Swift/Sample.xcodeproj/project.pbxproj

@@ -10,9 +10,10 @@
 		050E7C7419D22E19004363C2 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 050E7C7319D22E19004363C2 /* AppDelegate.swift */; };
 		050E7C7619D22E19004363C2 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 050E7C7519D22E19004363C2 /* ViewController.swift */; };
 		05DDD8DB19D2336300013C30 /* Default-568h@2x.png in Resources */ = {isa = PBXBuildFile; fileRef = 05DDD8DA19D2336300013C30 /* Default-568h@2x.png */; };
-		4690009EF79C47BBA8FDBAD4 /* libPods.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 2ACC614D420B4E90B7EE3BCE /* libPods.a */; };
 		6C5053DB19EE266A00E385DE /* Default-667h@2x.png in Resources */ = {isa = PBXBuildFile; fileRef = 6C5053D919EE266A00E385DE /* Default-667h@2x.png */; };
 		6C5053DC19EE266A00E385DE /* Default-736h@3x.png in Resources */ = {isa = PBXBuildFile; fileRef = 6C5053DA19EE266A00E385DE /* Default-736h@3x.png */; };
+		92E46E91A7D47AEC5B2B2F55 /* Pods.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 7FC29F18AE7C8C204A5CD4F2 /* Pods.framework */; };
+		CCB01CAB1C5FEA6E00CA64C4 /* TailLoadingCellNode.swift in Sources */ = {isa = PBXBuildFile; fileRef = CCB01CAA1C5FEA6E00CA64C4 /* TailLoadingCellNode.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -21,11 +22,11 @@
 		050E7C7319D22E19004363C2 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		050E7C7519D22E19004363C2 /* ViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ViewController.swift; sourceTree = "<group>"; };
 		05DDD8DA19D2336300013C30 /* Default-568h@2x.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; name = "Default-568h@2x.png"; path = "../Default-568h@2x.png"; sourceTree = "<group>"; };
-		05DDD8DC19D2341D00013C30 /* AsyncDisplayKit-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "AsyncDisplayKit-Bridging-Header.h"; sourceTree = "<group>"; };
-		2ACC614D420B4E90B7EE3BCE /* libPods.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libPods.a; sourceTree = BUILT_PRODUCTS_DIR; };
 		6C5053D919EE266A00E385DE /* Default-667h@2x.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = "Default-667h@2x.png"; sourceTree = SOURCE_ROOT; };
 		6C5053DA19EE266A00E385DE /* Default-736h@3x.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = "Default-736h@3x.png"; sourceTree = SOURCE_ROOT; };
+		7FC29F18AE7C8C204A5CD4F2 /* Pods.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		841652076B3E9351337AA7C7 /* Pods.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = Pods.debug.xcconfig; path = "Pods/Target Support Files/Pods/Pods.debug.xcconfig"; sourceTree = "<group>"; };
+		CCB01CAA1C5FEA6E00CA64C4 /* TailLoadingCellNode.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TailLoadingCellNode.swift; sourceTree = "<group>"; };
 		E3EE87D12CE3EF73FAE2EF02 /* Pods.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = Pods.release.xcconfig; path = "Pods/Target Support Files/Pods/Pods.release.xcconfig"; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
@@ -34,7 +35,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				4690009EF79C47BBA8FDBAD4 /* libPods.a in Frameworks */,
+				92E46E91A7D47AEC5B2B2F55 /* Pods.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -65,6 +66,7 @@
 		050E7C7019D22E19004363C2 /* Sample */ = {
 			isa = PBXGroup;
 			children = (
+				CCB01CAA1C5FEA6E00CA64C4 /* TailLoadingCellNode.swift */,
 				050E7C7319D22E19004363C2 /* AppDelegate.swift */,
 				050E7C7519D22E19004363C2 /* ViewController.swift */,
 				050E7C7119D22E19004363C2 /* Supporting Files */,
@@ -75,7 +77,6 @@
 		050E7C7119D22E19004363C2 /* Supporting Files */ = {
 			isa = PBXGroup;
 			children = (
-				05DDD8DC19D2341D00013C30 /* AsyncDisplayKit-Bridging-Header.h */,
 				050E7C7219D22E19004363C2 /* Info.plist */,
 				05DDD8DA19D2336300013C30 /* Default-568h@2x.png */,
 				6C5053D919EE266A00E385DE /* Default-667h@2x.png */,
@@ -87,7 +88,7 @@
 		092C2001FE124604891D6E90 /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
-				2ACC614D420B4E90B7EE3BCE /* libPods.a */,
+				7FC29F18AE7C8C204A5CD4F2 /* Pods.framework */,
 			);
 			name = Frameworks;
 			sourceTree = "<group>";
@@ -113,6 +114,7 @@
 				050E7C6B19D22E19004363C2 /* Frameworks */,
 				050E7C6C19D22E19004363C2 /* Resources */,
 				941C5E41C54B4613A2D3B760 /* Copy Pods Resources */,
+				1F5A9F09F5875F61862D0783 /* Embed Pods Frameworks */,
 			);
 			buildRules = (
 			);
@@ -131,7 +133,7 @@
 			attributes = {
 				LastSwiftMigration = 0700;
 				LastSwiftUpdateCheck = 0700;
-				LastUpgradeCheck = 0600;
+				LastUpgradeCheck = 0720;
 				ORGANIZATIONNAME = Facebook;
 				TargetAttributes = {
 					050E7C6D19D22E19004363C2 = {
@@ -171,6 +173,21 @@
 /* End PBXResourcesBuildPhase section */
 
 /* Begin PBXShellScriptBuildPhase section */
+		1F5A9F09F5875F61862D0783 /* Embed Pods Frameworks */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputPaths = (
+			);
+			name = "Embed Pods Frameworks";
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"${SRCROOT}/Pods/Target Support Files/Pods/Pods-frameworks.sh\"\n";
+			showEnvVarsInLog = 0;
+		};
 		941C5E41C54B4613A2D3B760 /* Copy Pods Resources */ = {
 			isa = PBXShellScriptBuildPhase;
 			buildActionMask = 2147483647;
@@ -208,6 +225,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				CCB01CAB1C5FEA6E00CA64C4 /* TailLoadingCellNode.swift in Sources */,
 				050E7C7619D22E19004363C2 /* ViewController.swift in Sources */,
 				050E7C7419D22E19004363C2 /* AppDelegate.swift in Sources */,
 			);
@@ -236,6 +254,7 @@
 				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
 				COPY_PHASE_STRIP = NO;
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				ENABLE_TESTABILITY = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_OPTIMIZATION_LEVEL = 0;
@@ -300,8 +319,8 @@
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				INFOPLIST_FILE = Sample/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
+				PRODUCT_BUNDLE_IDENTIFIER = "com.facebook.AsyncDisplayKit.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_OBJC_BRIDGING_HEADER = "Sample/AsyncDisplayKit-Bridging-Header.h";
 			};
 			name = Debug;
 		};
@@ -312,8 +331,8 @@
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				INFOPLIST_FILE = Sample/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
+				PRODUCT_BUNDLE_IDENTIFIER = "com.facebook.AsyncDisplayKit.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_OBJC_BRIDGING_HEADER = "Sample/AsyncDisplayKit-Bridging-Header.h";
 			};
 			name = Release;
 		};

examples/Swift/Sample.xcodeproj/xcshareddata/xcschemes/Sample.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0620"
+   LastUpgradeVersion = "0720"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -23,10 +23,10 @@
       </BuildActionEntries>
    </BuildAction>
    <TestAction
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      shouldUseLaunchSchemeArgsEnv = "YES"
+      shouldUseLaunchSchemeArgsEnv = "YES">
-      buildConfiguration = "Debug">
       <Testables>
       </Testables>
       <MacroExpansion>
@@ -38,15 +38,18 @@
             ReferencedContainer = "container:Sample.xcodeproj">
          </BuildableReference>
       </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
    </TestAction>
    <LaunchAction
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
-      buildConfiguration = "Debug"
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
       allowLocationSimulation = "YES">
       <BuildableProductRunnable
          runnableDebuggingMode = "0">
@@ -62,10 +65,10 @@
       </AdditionalOptions>
    </LaunchAction>
    <ProfileAction
+      buildConfiguration = "Release"
       shouldUseLaunchSchemeArgsEnv = "YES"
       savedToolIdentifier = ""
       useCustomWorkingDirectory = "NO"
-      buildConfiguration = "Release"
       debugDocumentVersioning = "YES">
       <BuildableProductRunnable
          runnableDebuggingMode = "0">

examples/Swift/Sample.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "group:Sample.xcodeproj">
+   </FileRef>
+   <FileRef
+      location = "group:Pods/Pods.xcodeproj">
+   </FileRef>
+</Workspace>

examples/Swift/Sample/AppDelegate.swift

@@ -19,7 +19,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
   func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
     let window = UIWindow(frame: UIScreen.mainScreen().bounds)
     window.backgroundColor = UIColor.whiteColor()
-    window.rootViewController = ViewController(nibName: nil, bundle: nil)
+    window.rootViewController = ViewController()
     window.makeKeyAndVisible()
     self.window = window
     return true

examples/Swift/Sample/AsyncDisplayKit-Bridging-Header.h

@@ -1,12 +0,0 @@
-/* This file provided by Facebook is for non-commercial testing and evaluation
- * purposes only.  Facebook reserves all rights not expressly granted.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
- * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
- * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
- * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-
-#import <AsyncDisplayKit/AsyncDisplayKit.h>

examples/Swift/Sample/Info.plist

@@ -7,7 +7,7 @@
 	<key>CFBundleExecutable</key>
 	<string>$(EXECUTABLE_NAME)</string>
 	<key>CFBundleIdentifier</key>
-	<string>com.facebook.AsyncDisplayKit.$(PRODUCT_NAME:rfc1034identifier)</string>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
 	<key>CFBundleInfoDictionaryVersion</key>
 	<string>6.0</string>
 	<key>CFBundleName</key>

examples/Swift/Sample/TailLoadingCellNode.swift

@@ -0,0 +1,53 @@
+//
+//  TailLoadingCellNode.swift
+//  Sample
+//
+//  Created by Adlai Holler on 2/1/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+import AsyncDisplayKit
+import UIKit
+
+final class TailLoadingCellNode: ASCellNode {
+  let spinner = SpinnerNode()
+  let text = ASTextNode()
+
+  override init() {
+    super.init()
+    addSubnode(text)
+    text.attributedString = NSAttributedString(
+      string: "Loading…",
+      attributes: [
+        NSFontAttributeName: UIFont.systemFontOfSize(12),
+        NSForegroundColorAttributeName: UIColor.lightGrayColor(),
+        NSKernAttributeName: -0.3
+      ])
+    addSubnode(spinner)
+  }
+
+  override func layoutSpecThatFits(constrainedSize: ASSizeRange) -> ASLayoutSpec {
+    return ASStackLayoutSpec(
+      direction: .Horizontal,
+      spacing: 16,
+      justifyContent: .Center,
+      alignItems: .Center,
+      children: [ text, spinner ])
+  }
+}
+
+final class SpinnerNode: ASDisplayNode {
+  var activityIndicatorView: UIActivityIndicatorView {
+    return view as! UIActivityIndicatorView
+  }
+
+  override init() {
+    super.init(viewBlock: { UIActivityIndicatorView(activityIndicatorStyle: .Gray) }, didLoadBlock: nil)
+    preferredFrameSize.height = 32
+  }
+
+  override func didLoad() {
+    super.didLoad()
+    activityIndicatorView.startAnimating()
+  }
+}

examples/Swift/Sample/ViewController.swift

@@ -10,57 +10,136 @@
  */
 
 import UIKit
+import AsyncDisplayKit
 
-class ViewController: UIViewController, ASTableViewDataSource, ASTableViewDelegate {
+final class ViewController: ASViewController, ASTableDataSource, ASTableDelegate {
 
-  var tableView: ASTableView
+  struct State {
+    var itemCount: Int
+    var fetchingMore: Bool
+    static let empty = State(itemCount: 20, fetchingMore: false)
+  }
 
+  enum Action {
+    case BeginBatchFetch
+    case EndBatchFetch(resultCount: Int)
+  }
 
-  // MARK: UIViewController.
+  var tableNode: ASTableNode {
+    return node as! ASTableNode
+  }
 
-  override required init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
+  private(set) var state: State = .empty
-    self.tableView = ASTableView()
 
-    super.init(nibName: nil, bundle: nil)
+  init() {
-
+    super.init(node: ASTableNode())
-    self.tableView.asyncDataSource = self
+    tableNode.delegate = self
-    self.tableView.asyncDelegate = self
+    tableNode.dataSource = self
   }
 
   required init?(coder aDecoder: NSCoder) {
     fatalError("storyboards are incompatible with truth and beauty")
   }
 
-  override func viewDidLoad() {
-    super.viewDidLoad()
-    self.view.addSubview(self.tableView)
-  }
-
-  override func viewWillLayoutSubviews() {
-    self.tableView.frame = self.view.bounds
-  }
-
   override func prefersStatusBarHidden() -> Bool {
     return true
   }
 
-
   // MARK: ASTableView data source and delegate.
 
-  func tableView(tableView: ASTableView!, nodeForRowAtIndexPath indexPath: NSIndexPath!) -> ASCellNode! {
+  func tableView(tableView: ASTableView, nodeForRowAtIndexPath indexPath: NSIndexPath) -> ASCellNode {
-    let patter = NSString(format: "[%ld.%ld] says hello!", indexPath.section, indexPath.row)
+    // Should read the row count directly from table view but
+    // https://github.com/facebook/AsyncDisplayKit/issues/1159
+    let rowCount = self.tableView(tableView, numberOfRowsInSection: 0)
+
+    if state.fetchingMore && indexPath.row == rowCount - 1 {
+      return TailLoadingCellNode()
+    }
+
     let node = ASTextCellNode()
-    node.text = patter as String
+    node.text = String(format: "[%ld.%ld] says hello!", indexPath.section, indexPath.row)
 
     return node
   }
 
-  func numberOfSectionsInTableView(tableView: UITableView!) -> Int {
+  func numberOfSectionsInTableView(tableView: UITableView) -> Int {
     return 1
   }
 
-  func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int {
+  func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-    return 20
+    var count = state.itemCount
+    if state.fetchingMore {
+      count += 1
+    }
+    return count
   }
 
+  func tableView(tableView: ASTableView, willBeginBatchFetchWithContext context: ASBatchContext) {
+    /// This call will come in on a background thread. Switch to main
+    /// to add our spinner, then fire off our fetch.
+    dispatch_async(dispatch_get_main_queue()) {
+      let oldState = self.state
+      self.state = ViewController.handleAction(.BeginBatchFetch, fromState: oldState)
+      self.renderDiff(oldState)
+    }
+
+    ViewController.fetchDataWithCompletion { resultCount in
+      let action = Action.EndBatchFetch(resultCount: resultCount)
+      let oldState = self.state
+      self.state = ViewController.handleAction(action, fromState: oldState)
+      self.renderDiff(oldState)
+      context.completeBatchFetching(true)
+    }
+  }
+
+  private func renderDiff(oldState: State) {
+    let tableView = tableNode.view
+    tableView.beginUpdates()
+
+    // Add or remove items
+    let rowCountChange = state.itemCount - oldState.itemCount
+    if rowCountChange > 0 {
+      let indexPaths = (oldState.itemCount..<state.itemCount).map { index in
+        NSIndexPath(forRow: index, inSection: 0)
+      }
+      tableView.insertRowsAtIndexPaths(indexPaths, withRowAnimation: .None)
+    } else if rowCountChange < 0 {
+      assertionFailure("Deleting rows is not implemented. YAGNI.")
+    }
+
+    // Add or remove spinner.
+    if state.fetchingMore != oldState.fetchingMore {
+      if state.fetchingMore {
+        // Add spinner.
+        let spinnerIndexPath = NSIndexPath(forRow: state.itemCount, inSection: 0)
+        tableView.insertRowsAtIndexPaths([ spinnerIndexPath ], withRowAnimation: .None)
+      } else {
+        // Remove spinner.
+        let spinnerIndexPath = NSIndexPath(forRow: oldState.itemCount, inSection: 0)
+        tableView.deleteRowsAtIndexPaths([ spinnerIndexPath ], withRowAnimation: .None)
+      }
+    }
+    tableView.endUpdatesAnimated(false, completion: nil)
+  }
+
+  /// (Pretend) fetches some new items and calls the
+  /// completion handler on the main thread.
+  private static func fetchDataWithCompletion(completion: (Int) -> Void) {
+    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(NSTimeInterval(NSEC_PER_SEC) * 0.5))
+    dispatch_after(time, dispatch_get_main_queue()) {
+      let resultCount = Int(arc4random_uniform(20))
+      completion(resultCount)
+    }
+  }
+
+  private static func handleAction(action: Action, var fromState state: State) -> State {
+    switch action {
+    case .BeginBatchFetch:
+      state.fetchingMore = true
+    case let .EndBatchFetch(resultCount):
+      state.itemCount += resultCount
+      state.fetchingMore = false
+    }
+    return state
+  }
 }