Add method for reload data without passing initial item

When using PagingViewControllerDataSource we can reload data without knowing the initial item, as we can just select the previously selected item or the first in the list. This makes it much easier to reload data in most use cases.
rechsteiner · Mar 25, 2018 · 8ebd931 · 8ebd931
1 parent 07641e2
commit 8ebd931
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Showing 7 changed files with 162 additions and 12 deletions.
diff --git a/IconsExample/ViewController.swift b/IconsExample/ViewController.swift
@@ -24,8 +24,7 @@ struct IconItem: PagingItem, Hashable, Comparable {
   static func ==(lhs: IconItem, rhs: IconItem) -> Bool {
     return (
       lhs.index == rhs.index &&
-      lhs.icon == rhs.icon &&
-      lhs.image == rhs.image
+      lhs.icon == rhs.icon
     )
   }
 }

diff --git a/Parchment/Classes/EMPageViewController.swift b/Parchment/Classes/EMPageViewController.swift
@@ -215,7 +215,12 @@ open class EMPageViewController: UIViewController, UIScrollViewDelegate {
         }
 
     }
-
+
+    open func removeAllViewControllers() {
+        self.removeChildIfNeeded(beforeViewController)
+        self.removeChildIfNeeded(selectedViewController)
+        self.removeChildIfNeeded(afterViewController)
+    }
 
     /**
      Transitions to the view controller right of the currently selected view controller in a horizontal orientation, or below the currently selected view controller in a vertical orientation. Also described as going to the next page.

diff --git a/Parchment/Classes/PagingStateMachine.swift b/Parchment/Classes/PagingStateMachine.swift
@@ -36,6 +36,8 @@ class PagingStateMachine<T: PagingItem> where T: Equatable {
       handleTransitionSizeEvent(event)
     case .cancelScrolling:
       handleCancelScrollingEvent(event)
+    case .removeAll:
+      handleRemoveAllEvent(event)
     }
   }
 
@@ -179,4 +181,9 @@ class PagingStateMachine<T: PagingItem> where T: Equatable {
     }
   }
 
+  private func handleRemoveAllEvent(_ event: PagingEvent<T>) {
+    let oldState = state
+    state = .empty
+    onStateChange?(oldState, state, event)
+  }
 }
diff --git a/Parchment/Classes/PagingViewController.swift b/Parchment/Classes/PagingViewController.swift
@@ -313,10 +313,32 @@ open class PagingViewController<T: PagingItem>:
 
   // MARK: Public Methods
 
+  /// Reload data for all the menu items. This will keep the
+  /// previously selected item if it's still part of the updated data.
+  /// If not, it will select the first item in the list. This method
+  /// will not work when using PagingViewControllerInfiniteDataSource
+  /// as we then need to know what the initial item should be. You
+  /// should use the reloadData(around:) method in that case.
+  open func reloadData() {
+    let previouslySelected = state.currentPagingItem
+    let items = generateItemsForIndexedDataSource()
+    indexedDataSource?.items = items
+
+    if let pagingItem = items.first(where: { $0 == previouslySelected }) {
+      select(pagingItem: pagingItem, animated: false)
+    } else if let firstItem = items.first {
+      select(pagingItem: firstItem, animated: false)
+    } else {
+      stateMachine.fire(.removeAll)
+    }
+  }
+
   /// Reload data around given paging item. This will set the given
   /// paging item as selected and generate new items around it. This
   /// will also reload the view controllers displayed in the page view
-  /// controller.
+  /// controller. You need to use this method to reload data when
+  /// using PagingViewControllerInfiniteDataSource as we need to know
+  /// the initial item.
   ///
   /// - Parameter pagingItem: The `PagingItem` that will be selected
   /// after the data reloads.
@@ -640,7 +662,7 @@ open class PagingViewController<T: PagingItem>:
 
       collectionViewLayout.invalidateLayout(with: invalidationContext)
     case .empty:
-      break
+      removeAll()
     }
   }
 
@@ -695,6 +717,13 @@ open class PagingViewController<T: PagingItem>:
     return items
   }
 
+  private func removeAll() {
+    visibleItems = PagingItems(items: [])
+    collectionViewLayout.visibleItems = visibleItems
+    pageViewController.removeAllViewControllers()
+    collectionView.reloadData()
+  }
+
   private func reloadItems(around pagingItem: T, keepExisting: Bool = false) {
     var toItems = generateItems(around: pagingItem)
 

diff --git a/Parchment/Enums/PagingEvent.swift b/Parchment/Enums/PagingEvent.swift
@@ -8,6 +8,7 @@ enum PagingEvent<T: PagingItem> where T: Equatable {
   case transitionSize
   case cancelScrolling
   case reload(contentOffset: CGPoint)
+  case removeAll
 }
 
 extension PagingEvent {

diff --git a/ParchmentTests/PagingViewControllerSpec.swift b/ParchmentTests/PagingViewControllerSpec.swift
@@ -40,13 +40,108 @@ class DeinitFixedPagingViewController: FixedPagingViewController {
   deinit { deinitCalled?() }
 }
 
+class ReloadingDataSource: PagingViewControllerDataSource {
+  var items: [PagingIndexItem] = []
+
+  func numberOfViewControllers<T>(in pagingViewController: PagingViewController<T>) -> Int {
+    return items.count
+  }
+
+  func pagingViewController<T>(_ pagingViewController: PagingViewController<T>, viewControllerForIndex index: Int) -> UIViewController {
+    return UIViewController()
+  }
+
+  func pagingViewController<T>(_ pagingViewController: PagingViewController<T>, pagingItemForIndex index: Int) -> T {
+    return items[index] as! T
+  }
+}
+
 class PagingViewControllerSpec: QuickSpec {
 
   override func spec() {
 
-    xdescribe("PagingViewController") {
+    describe("PagingViewController") {
+
+      describe("reloading data") {
+
+        let dataSource = ReloadingDataSource()
+        var viewController: PagingViewController<PagingIndexItem>!
+
+        beforeEach {
+          dataSource.items = [
+            PagingIndexItem(index: 0, title: "First"),
+            PagingIndexItem(index: 1, title: "Second")
+          ]
+
+          viewController = PagingViewController()
+          viewController.menuItemSize = .fixed(width: 100, height: 50)
+          viewController.dataSource = dataSource
+
+          UIApplication.shared.keyWindow!.rootViewController = viewController
+          let _ = viewController.view
+
+          viewController.collectionView.bounds = CGRect(x: 0, y: 0, width: 1000, height: 50)
+          viewController.viewDidLayoutSubviews()
+        }
+
+        it("reloads data around item") {
+          let first = PagingIndexItem(index: 2, title: "Third")
+          let third = PagingIndexItem(index: 3, title: "Fourth")
+          dataSource.items = [first, third]
+          viewController.reloadData(around: first)
+
+          let cell1 = viewController.collectionView.cellForItem(at: IndexPath(item: 0, section: 0)) as! PagingTitleCell
+          let cell2 = viewController.collectionView.cellForItem(at: IndexPath(item: 1, section: 0)) as! PagingTitleCell
+
+          expect(cell1.titleLabel.text).to(equal("Third"))
+          expect(cell2.titleLabel.text).to(equal("Fourth"))
+        }
+
+        it("selects previously selected item when reloading data") {
+          let first = PagingIndexItem(index: 0, title: "First")
+          let second = PagingIndexItem(index: 1, title: "Second")
+          let third = PagingIndexItem(index: 2, title: "Third")
+
+          viewController.select(index: 1)
+          dataSource.items = [first, second, third]
+          viewController.reloadData()
+
+          let cell1 = viewController.collectionView.cellForItem(at: IndexPath(item: 0, section: 0)) as! PagingTitleCell
+          let cell2 = viewController.collectionView.cellForItem(at: IndexPath(item: 1, section: 0)) as! PagingTitleCell
+          let cell3 = viewController.collectionView.cellForItem(at: IndexPath(item: 2, section: 0)) as! PagingTitleCell
+
+          expect(cell1.titleLabel.text).to(equal("First"))
+          expect(cell2.titleLabel.text).to(equal("Second"))
+          expect(cell3.titleLabel.text).to(equal("Third"))
+          expect(viewController.state).to(equal(PagingState.selected(pagingItem: second)))
+        }
+
+        it("selects the first item when reloading data with all new items") {
+          let third = PagingIndexItem(index: 2, title: "Third")
+          let fourth = PagingIndexItem(index: 3, title: "Fourth")
+
+          viewController.select(index: 1)
+          dataSource.items = [third, fourth]
+          viewController.reloadData()
+
+          let cell1 = viewController.collectionView.cellForItem(at: IndexPath(item: 0, section: 0)) as! PagingTitleCell
+          let cell2 = viewController.collectionView.cellForItem(at: IndexPath(item: 1, section: 0)) as! PagingTitleCell
+
+          expect(cell1.titleLabel.text).to(equal("Third"))
+          expect(cell2.titleLabel.text).to(equal("Fourth"))
+          expect(viewController.state).to(equal(PagingState.selected(pagingItem: third)))
+        }
+
+        fit("display an empty view after reloading data with no items") {
+          dataSource.items = []
+          viewController.reloadData()
+
+          expect(viewController.pageViewController.scrollView.subviews).to(beEmpty())
+          expect(viewController.collectionView.numberOfItems(inSection: 0)).to(equal(0))
+        }
+      }
 
-      describe("reloading items") {
+      describe("selecting items") {
 
         let dataSource = DataSource()
         var viewController: PagingViewController<Item>!
@@ -60,21 +155,22 @@ class PagingViewControllerSpec: QuickSpec {
           let _ = viewController.view
 
           viewController.collectionView.bounds = CGRect(x: 0, y: 0, width: 1000, height: 50)
+          viewController.viewDidLayoutSubviews()
         }
 
-        it("reloadItems: at begining") {
+        it("selecting the first item generates enough items") {
           viewController.select(pagingItem: Item(index: 0))
           let items = viewController.collectionView.numberOfItems(inSection: 0)
           expect(items).to(equal(21))
         }
 
-        it("reloadItems: at center") {
+        it("selecting the center item generates enough items") {
           viewController.select(pagingItem: Item(index: 20))
           let items = viewController.collectionView.numberOfItems(inSection: 0)
           expect(items).to(equal(21))
         }
 
-        it("reloadItems: at end") {
+        it("selecting the last item generates enough items") {
           viewController.select(pagingItem: Item(index: 50))
           let items = viewController.collectionView.numberOfItems(inSection: 0)
           expect(items).to(equal(21))

diff --git a/README.md b/README.md
@@ -138,13 +138,26 @@ func select(index: Int, animated: Bool = false)
 
 ## Reload data
 
-You can reload data for a given `PagingItem`:
+You can reload data using this method:
+
+```Swift
+func reloadData()
+```
+
+This will keep the previously selected item if it's still part of the
+updated data. If not, it will select the first item in the list. It
+will also reload the view controllers displayed in the page view
+controller.
+
+Calling `reloadData()` will not work when using
+`PagingViewControllerInfiniteDataSource`, as we then need to know what
+the initial item should be. In that case you should use this method:
 
 ```Swift
 func reloadData(around: PagingItem)
 ```
 
-This will mark the given paging item as selected and generate new items around it. It will also reload the view controllers displayed in the page view controller.
+This will mark the given paging item as selected and generate new items around it.
 
 ## Delegate