swift - 将变量从 Gesture Recognizer 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 会出现一个弹出式 UIView，其中包含一个 TextField 和一个将其保存在相应的 array 中的选项到单元格。

这是代码(按钮和手势已正确添加到viewDidLoad()方法中):

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 View Controller 中定义一个变量，希望该函数返回值并将其保存在全局变量中。 但是，后来从Apple那里发现 “函数的访问级别不能高于其参数类型和返回类型，因为该函数可以在其构成类型对周围代码不可用的情况下使用。” 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在长按手势功能中，以便轻松获得它的返回值。但是，我无法调用 Selector 函数，因为它在另一个函数中。

• 此外，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 longPressedPoint 被检测为在 Save 按钮内。因此，indexPathOfLongPressedCell 为 nil，应用程序崩溃。

谁能帮帮我...

Answer 1

假设您想要获取所选单元格的行并将其分配给全局变量 rowOfLongPressedItem，您不需要让 handleLongPress 返回一个 Int。

注意:这是一段 Swift 3 代码(概念相同):

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)")
}

此外，您不需要让 saveNoteButtonTapped 获取 rowOfLongPressedItem 参数。注意 rowOfLongPressedItem 是可选的，你应该确保它不是仍然为 nil(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
}