swift - 尝试在 TableView 中快速查找特定单元格时失败

Question

我想在我的 TableView 中找到特定的单元格类。我使用以下代码:

func setConfirmEnabledIfNeed(){
        let ip = IndexPath(row: 8, section: 0)
        if let cell = tableView.cellForRow(at: ip) as? ConfirmBtnCell {
            print("find confirm cell")
        }
        let c = tableView.cellForRow(at: ip) as? ConfirmBtnCell
        print("type of cell \(type(of: c))")
    }

print("find confirm cell") 从未被调用，但是，第二个打印输出:type of cell Optional<ConfirmBtnCell> ，显然是我需要的。但是为什么不调用 first print 呢？

我的行单元格如下所示:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let item = viewModel.items[indexPath.row]
    switch item {
    case .selectable(let value, let placeholder, let type):
        let selectionCell = tableView.dequeueReusableCell(withIdentifier: "SelectionCell") as! SelectionCell
        if let placeholder = placeholder { selectionCell.setPlaceholder(placeholder) }
        if let text = value as? String, !text.isEmpty { selectionCell.hidePlaceholder();
            selectionCell.textLbl.text = text }
        if let date = value as? Date { selectionCell.hidePlaceholder();
            selectionCell.textLbl.text = DateFormatterUtil.getReadableStringFromDate(date) }
        return selectionCell
    case .back:
        return tableView.dequeueReusableCell(withIdentifier: "BackBtnCell") as! BackBtnCell
    case .confirm:
        return tableView.dequeueReusableCell(withIdentifier: "ConfirmBtnCell") as! ConfirmBtnCell
    case .editableNumbers(let text, let placeholder, let type):
        let editableCell = tableView.dequeueReusableCell(withIdentifier: "TextEditCell") as! TextEditCell
        editableCell.setup(isNumerical: true)
        if let placeholder = placeholder { editableCell.setPlaceholder(placeholder) }
        if let text = text {editableCell.hidePlaceholder(); editableCell.txtf.text = text }
        editableCell.textChanged = {[weak self] text in
            guard let text = text else { return }
            if type == .sumCash {
                self?.viewModel.collectedInfo[CorrectionChequeViewModel.infoKeys.sumCash.rawValue] = text
                self?.setConfirmEnabledIfNeed()
            }

            if type == .sumElectronic {
                self?.viewModel.collectedInfo[CorrectionChequeViewModel.infoKeys.sumElectronic.rawValue] = text
            }
        }
        return editableCell
    case .editableText(let text, let placeholder, let type):
        let editableCell = tableView.dequeueReusableCell(withIdentifier: "TextEditCell") as! TextEditCell
        editableCell.setup(isNumerical: false)
        if let placeholder = placeholder { editableCell.setPlaceholder(placeholder) }
        if let text = text {editableCell.hidePlaceholder(); editableCell.txtf.text = text }
        editableCell.textChanged = {[weak self] text in
            guard let text = text else { return }
            if type == .sumCash {
                self?.viewModel.collectedInfo[CorrectionChequeViewModel.infoKeys.description.rawValue] = text
            }

            if type == .sumElectronic {
                self?.viewModel.collectedInfo[CorrectionChequeViewModel.infoKeys.number.rawValue] = text
            }
        }
        return editableCell
     default:
        return UITableViewCell()
    }
}

更新:我发现如果不从 TableView cellForRow 方法调用代码，它就可以工作。我尝试使用 dispatch_after 启动该代码块，它起作用了。

Answer 1

在你的if语句，tableView.cellForRow(at: ip) as? ConfirmBtnCell 的值是零，所以你永远不会进入 block 。

在第二条语句(let c = tableView.cellForRow(at: ip) as? ConfirmBtnCell)中，c 的值是一个 Optional<ConfirmBtnCell> .如果你解包可选的，你会看到它的解包值也是一个 nil。

如果您的行不可见，tableView.cellForRow即使设置了单元格，也会返回 nil。查看Apple Documentation .