More progress with the Swift example

examples/Swift/Sample/ViewController.swift

@@ -14,10 +14,23 @@ import AsyncDisplayKit
 
 final class ViewController: ASViewController, ASTableDataSource, ASTableDelegate {
 
+  struct State {
+    var rowCount: Int
+    var showingSpinner: Bool
+    static let empty = State(rowCount: 20, showingSpinner: false)
+  }
+
+  enum Action {
+    case BeginBatchFetch
+    case EndBatchFetch(resultCount: Int)
+  }
+
   var tableNode: ASTableNode {
     return node as! ASTableNode
   }
 
+  private(set) var state: State = .empty
+
   init() {
     super.init(node: ASTableNode())
     tableNode.delegate = self
@@ -35,6 +48,11 @@ final class ViewController: ASViewController, ASTableDataSource, ASTableDelegate
   // MARK: ASTableView data source and delegate.
 
   func tableView(tableView: ASTableView, nodeForRowAtIndexPath indexPath: NSIndexPath) -> ASCellNode {
+    NSLog("Number of rows %d", tableView.numberOfRowsInSection(0))
+    if state.showingSpinner && indexPath.row == tableView.numberOfRowsInSection(0) - 1 {
+      return TailLoadingCellNode()
+    }
+
     let node = ASTextCellNode()
     node.text = String(format: "[%ld.%ld] says hello!", indexPath.section, indexPath.row)
 
@@ -46,7 +64,70 @@ final class ViewController: ASViewController, ASTableDataSource, ASTableDelegate
   }
 
   func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-    return 20
+    var count = state.rowCount
+    if state.showingSpinner {
+      count += 1
+    }
+    return count
   }
 
+  func tableView(tableView: ASTableView, willBeginBatchFetchWithContext context: ASBatchContext) {
+    context.cancelBatchFetching()
+    dispatch_async(dispatch_get_main_queue()) {
+      let oldState = self.state
+      self.state = ViewController.handleAction(.BeginBatchFetch, fromState: oldState)
+      self.render(oldState)
+    }
+    return;
+
+    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(NSTimeInterval(NSEC_PER_SEC) * 3))
+    dispatch_after(time, dispatch_get_main_queue()) {
+      let action = Action.EndBatchFetch(resultCount: 20)
+      let oldState = self.state
+      self.state = ViewController.handleAction(action, fromState: oldState)
+      self.render(oldState)
+    	context.completeBatchFetching(true)
+    }
+  }
+
+  func render(oldState: State) {
+    let tableView = tableNode.view
+    tableView.beginUpdates()
+
+    // Add or remove items
+    let rowCountChange = state.rowCount - oldState.rowCount
+    if rowCountChange > 0 {
+      let indexPaths = (oldState.rowCount..<state.rowCount).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.showingSpinner && !oldState.showingSpinner {
+      if state.showingSpinner {
+        // Add spinner.
+        let spinnerIndexPath = NSIndexPath(forRow: state.rowCount, inSection: 0)
+        tableView.insertRowsAtIndexPaths([ spinnerIndexPath ], withRowAnimation: .None)
+      } else {
+        // Remove spinner.
+        let spinnerIndexPath = NSIndexPath(forRow: oldState.rowCount, inSection: 0)
+        tableView.deleteRowsAtIndexPaths([ spinnerIndexPath ], withRowAnimation: .None)
+      }
+    }
+    tableView.endUpdatesAnimated(false, completion: nil)
+  }
+
+  static func handleAction(action: Action, var fromState state: State) -> State {
+    switch action {
+    case .BeginBatchFetch:
+      state.showingSpinner = true
+    case let .EndBatchFetch(resultCount):
+      state.rowCount += resultCount
+      state.showingSpinner = false
+    }
+    return state
+  }
 }