将变量从手势识别器函数传递到 IBAction

Question

我有一个简单的应用程序，其中包含 CollectionView 和项目。 长按cell 时，弹出UIView 会出现TextField 和将其保存在与cell 对应的array 中的选项。

这是代码（buttons 和 gestures 已在 viewDidLoad() 方法中正确添加）：

class CollectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate  {
var longPressedPoint: CGPoint?

public var rowOfLongPressedItem: Int? = nil

func handleLongPress(longPressRecognizer: UILongPressGestureRecognizer)  -> Int      {
    print("LONG PRESS Gesture Recognized")
    notePopup.hidden = false
    longPressedPoint =  longPressRecognizer.locationInView(longPressRecognizer.view)
    var indexPathOfLongPressedCell = self.itemCollectionView.indexPathForItemAtPoint(longPressedPoint!)
    rowOfLongPressedItem = (indexPathOfLongPressedCell?.row)
    print("rowOfLongPressedItem -> .\(rowOfLongPressedItem)")
    return rowOfLongPressedItem!
}

func saveNoteButtonTapped(rowOfLongPressedItem: Int) {
    print("rowOfLongPressedItem when Save button is tapped -> .\(rowOfLongPressedItem)")       

    //Can’t go further down as rowOfLongPressedItem is NOT available from “handleLongPress” function…

    var selectedItem = ItemsList[rowOfLongPressedItem]
    selectedItem.counts += 1
    var latest = selectedItem.counts - 1
    selectedItem.timestamp.append(NSDate())
    selectedItem.note.append(noteTextField.text)
    ItemsList[rowOfLongPressedItem] = selectedItem
    print(".\(selectedItem.title) has been tapped .\(selectedItem.counts)")
    print("The latest tap on .\(selectedItem.title) is at .\(selectedItem.timestamp[latest])")
    print("The note .\(noteTextField.text) has been added")
    notePopup.hidden = true
}
}

尝试通过几种方式解决问题：

• 在视图控制器中定义一个变量，希望该函数将返回值并将其保存在全局变量中。 但是，后来从苹果那里发现 “一个函数的访问级别不能高于其参数类型和返回类型，因为该函数可用于其组成类型对周围代码不可用的情况。” https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/AccessControl.html

• 我尝试将按钮的选择器功能代码放入长按手势功能中，以便轻松获得它的返回值。但是，我无法调用 Selector 函数，因为它位于另一个函数中。

• 另外，我尝试返回长按手势功能的值并在保存按钮的 IBAction 中使用它。但是，为此我需要再次调用handleLongPress，然后将longPressedPoint 检测为内部保存按钮。因此，indexPathOfLongPressedCell 是 nil，应用程序崩溃。

谁能帮帮我...

Answer 1

假设您要获取所选单元格的行并将其分配给全局变量rowOfLongPressedItem，则无需让handleLongPress 返回一个Int。

注意：这是一个 Swift 3 代码（具有相同的概念）：

public var rowOfLongPressedItem: Int? = nil

override func viewDidLoad() {
    //...

    let longPressRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(ViewController.assignRowOfLongPressedItem))

    itemCollectionView.addGestureRecognizer(longPressRecognizer)

    //...
}

func assignRowOfLongPressedItem(longPressRecognizer: UILongPressGestureRecognizer) {
    let longPressedPoint = longPressRecognizer.location(in: longPressRecognizer.view)
    var indexPathOfLongPressedCell = self.itemCollectionView.indexPathForItem(at: longPressedPoint)
    rowOfLongPressedItem = (indexPathOfLongPressedCell?.row)
    // if you long press the first row -for example-, the output should be: "rowOfLongPressedItem -> .Optional(0)"
    print("rowOfLongPressedItem -> .\(rowOfLongPressedItem)")
}

另外，你不需要让saveNoteButtonTapped 带rowOfLongPressedItem 参数。注意rowOfLongPressedItem 是可选的，你应该确保它不是仍然为零（你可以使用Early Exit 方法）：

func saveNoteButtonTapped(sender: UIButton) {
        guard let selectedCellRow = rowOfLongPressedItem else {
            print("rowOfLongPressedItem is nil!!")
            return
        }

        print("rowOfLongPressedItem when Save button is tapped -> .\(selectedCellRow)")
        var selectedItem = ItemsList[selectedCellRow]

        selectedItem.counts += 1
        var latest = selectedItem.counts - 1
        selectedItem.timestamp.append(NSDate())
        selectedItem.note.append(noteTextField.text)
        ItemsList[row] = selectedItem
        print(".\(selectedItem.title) has been tapped .\(selectedItem.counts)")
        print("The latest tap on .\(selectedItem.title) is at .\(selectedItem.timestamp[latest])")
        print("The note .\(noteTextField.text) has been added")
        notePopup.hidden = true
}

Answer 2

rowOfLongPressedItem 可用于这两个函数。您无需将其设为saveNoteButtonTapped 的参数。

var rowOfLongPressedItem: Int? = nil

func handleLongPress(longPressRecognizer: UILongPressGestureRecognizer)  -> Int      {
    print("LONG PRESS Gesture Recognized")
    notePopup.hidden = false
    longPressedPoint =  longPressRecognizer.locationInView(longPressRecognizer.view)
    var indexPathOfLongPressedCell = self.itemCollectionView.indexPathForItemAtPoint(longPressedPoint!)
    rowOfLongPressedItem = (indexPathOfLongPressedCell?.row)
    print("rowOfLongPressedItem -> .\(rowOfLongPressedItem)")
    return rowOfLongPressedItem!
}

func saveNoteButtonTapped() {

    guard let row = rowOfLongPressedItem else {
        return // rowOfLongPressedItem was nil
    }

    print("rowOfLongPressedItem when Save button is tapped -> .\(row)")
    var selectedItem = ItemsList[row]

    selectedItem.counts += 1
    var latest = selectedItem.counts - 1
    selectedItem.timestamp.append(NSDate())
    selectedItem.note.append(noteTextField.text)
    ItemsList[row] = selectedItem
    print(".\(selectedItem.title) has been tapped .\(selectedItem.counts)")
    print("The latest tap on .\(selectedItem.title) is at .\(selectedItem.timestamp[latest])")
    print("The note .\(noteTextField.text) has been added")
    notePopup.hidden = true
}