ios - 如何在 cellForRowAt Swift 之外修改单元格

Question

目前我的代码是这样的，我在单元格中设置了一个日期选择器

代码 A 有效

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = Bundle.main.loadNibNamed("DailyTimesTableViewCell", owner: self, options: nil)?.first as! DailyTimesTableViewCell
    cell.endTimeTapped = { (button) -> DailyTimesTableViewCell in
        cell.datePicker.date = self.convertToDateObject(timeString: endTime as! String)
    } 
    return cell
}

我想根据一些逻辑修改单元格中的 datePicker，所以当我尝试下面的代码 B 时，使用回调 setTimeInDatePicker 修改单元格中的 datePicker 似乎没有去工作。

请告诉我哪里可能出错。

代码 B:不起作用

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = Bundle.main.loadNibNamed("DailyTimesTableViewCell", owner: self, options: nil)?.first as! DailyTimesTableViewCell
    cell.endTimeTapped = { (button) -> DailyTimesTableViewCell in
    self.setTimeInDatePicker(time: endTime!, cell: cell){ modifiedCell in
                    return modifiedCell
                }
    } 
    return cell
}


func setTimeInDatePicker(time: String, cell: DailyTimesTableViewCell, completionHandler: @escaping(DailyTimesTableViewCell) -> DailyTimesTableViewCell) {

    tableView.beginUpdates()
    let row     = cell.tag
    let rows    = self.timesArray.count

    if self.startTimeHighlighted{
        // Setting minimum startTime for datePicker
        if row == 0{ // For first row
            let minStartTimeString      =   "0:05 am"
            cell.datePicker.minimumDate = self.convertToDateObject(timeString: minStartTimeString)
        }
        else if row > 0 {   // For remaining rows
            let endTimeStringOfPreviousCell = self.timesArray[row - 1]["endTime"]!
            let endTimeObjectOfPreviousCell = self.convertToDateObject(timeString: endTimeStringOfPreviousCell)
            cell.datePicker.minimumDate     = endTimeObjectOfPreviousCell
        }

        // Setting maximum startTime for datepicker
        let endTimeString           =   self.timesArray[row]["endTime"]!
        let endTimeObject           =   self.convertToDateObject(timeString: endTimeString)
        let maxStartTimeObject      =   endTimeObject.addingTimeInterval(-5 * 60.0)            // removing 5mins
        cell.datePicker.maximumDate =   maxStartTimeObject

        // Setting selected date in as startTime title
        let dateString = self.convertDateToString(cell.datePicker.date)
        cell.startTime.setTitle(dateString, for: .normal)

        // Saving updated date to the timesArray
        self.timesArray[row]["startTime"] = dateString
        //print("endTime in DatePickerChanged: \(self.timesArray[row]["endTime"])")
        print("timesArray when startTimeHighlighted: \(self.timesArray)")
        completionHandler(cell)

    }
    else if self.endTimeHighlighted{
        print("datePicker changed 3")
        // Setting minimum endTime for datePicker

        let startTimeString = self.timesArray[row]["startTime"]
        let startTimeObject       =   self.convertToDateObject(timeString: startTimeString!)
        let minEndTimeObject    =   startTimeObject.addingTimeInterval(5 * 60.0)            // adding 5mins
        cell.datePicker.minimumDate = minEndTimeObject

        // Setting maximum endTime for datePicker
        if rows == 1 || row + 1 == self.timesArray.count{ // For first and last row
            let maxEndTimeString = "11:55 pm"
            cell.datePicker.maximumDate = self.convertToDateObject(timeString: maxEndTimeString)
        }
        else{ // If more than one row
            let nextCellStartTime           =   self.timesArray[row + 1]["startTime"]!
            let nextCellStartTimeObject     =   self.convertToDateObject(timeString: nextCellStartTime)
            cell.datePicker.maximumDate     =   nextCellStartTimeObject
        }

        // Setting selected date in as endTime title
        let dateString = self.convertDateToString(cell.datePicker.date)
        cell.endTime.setTitle(dateString, for: .normal)

        // Saving updated date to the timesArray
        self.timesArray[row]["endTime"] = dateString
        print("timesArray when endTimeHighlighted: \(self.timesArray)")

        completionHandler(cell)

    }

    tableView.endUpdates()

}

Answer 1

您似乎将 completionHandlers 与其他东西混淆了。

通常在任务异步时使用 completionHandlers。所以简而言之，您开始一项任务(通常是网络)，当它完成时(这可能需要很长时间)，您有一个处理程序可以调用以让应用程序知道它已完成。

由于应用程序没有等待这个非常长的异步任务完成，它继续运行并且与任务首次启动时的状态不同。简而言之，无论您在完成处理程序中返回什么，都将/不应使用。

基于此，以及一切似乎都是同步的事实，您可以像这样重构您的函数:

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = Bundle.main.loadNibNamed("DailyTimesTableViewCell", owner: self, options: nil)?.first as! DailyTimesTableViewCell
    cell.endTimeTapped = { [unowned self](_) in
        // Use unowned to make sure you don't create a retain-cycle
        self.setTimeInDatePicker(time: endTime!, cell: cell)
    } 
    return cell
}


func setTimeInDatePicker(time: String, cell: DailyTimesTableViewCell) {

    let row     = cell.tag
    let rows    = self.timesArray.count

    if self.startTimeHighlighted{
        // Setting minimum startTime for datePicker
        if row == 0{ // For first row
            let minStartTimeString      =   "0:05 am"
            cell.datePicker.minimumDate = self.convertToDateObject(timeString: minStartTimeString)
        }
        else if row > 0 {   // For remaining rows
            let endTimeStringOfPreviousCell = self.timesArray[row - 1]["endTime"]!
            let endTimeObjectOfPreviousCell = self.convertToDateObject(timeString: endTimeStringOfPreviousCell)
            cell.datePicker.minimumDate     = endTimeObjectOfPreviousCell
        }

        // Setting maximum startTime for datepicker
        let endTimeString           =   self.timesArray[row]["endTime"]!
        let endTimeObject           =   self.convertToDateObject(timeString: endTimeString)
        let maxStartTimeObject      =   endTimeObject.addingTimeInterval(-5 * 60.0)            // removing 5mins
        cell.datePicker.maximumDate =   maxStartTimeObject

        // Setting selected date in as startTime title
        let dateString = self.convertDateToString(cell.datePicker.date)
        cell.startTime.setTitle(dateString, for: .normal)

        // Saving updated date to the timesArray
        self.timesArray[row]["startTime"] = dateString
        //print("endTime in DatePickerChanged: \(self.timesArray[row]["endTime"])")
        print("timesArray when startTimeHighlighted: \(self.timesArray)")

    }
    else if self.endTimeHighlighted{
        print("datePicker changed 3")
        // Setting minimum endTime for datePicker

        let startTimeString = self.timesArray[row]["startTime"]
        let startTimeObject       =   self.convertToDateObject(timeString: startTimeString!)
        let minEndTimeObject    =   startTimeObject.addingTimeInterval(5 * 60.0)            // adding 5mins
        cell.datePicker.minimumDate = minEndTimeObject

        // Setting maximum endTime for datePicker
        if rows == 1 || row + 1 == self.timesArray.count{ // For first and last row
            let maxEndTimeString = "11:55 pm"
            cell.datePicker.maximumDate = self.convertToDateObject(timeString: maxEndTimeString)
        }
        else{ // If more than one row
            let nextCellStartTime           =   self.timesArray[row + 1]["startTime"]!
            let nextCellStartTimeObject     =   self.convertToDateObject(timeString: nextCellStartTime)
            cell.datePicker.maximumDate     =   nextCellStartTimeObject
        }

        // Setting selected date in as endTime title
        let dateString = self.convertDateToString(cell.datePicker.date)
        cell.endTime.setTitle(dateString, for: .normal)

        // Saving updated date to the timesArray
        self.timesArray[row]["endTime"] = dateString
        print("timesArray when endTimeHighlighted: \(self.timesArray)")

    }

}

请注意 endTimeTapped 闭包如何使 [unowned self] 的用户避免保留循环。

您还可以注意到 beginUpdate/endUpdate 已被删除。原因是您没有做任何影响相关单元格高度的事情，您只是更改日期，因此您不需要触发 tableView 的刷新，因为更改将自动应用。

检查这是否对您有所帮助？!

注意单元格是一个类，您作为参数发送给 setTimeInDatePicker 的是对它的引用，因此您实际上不需要返回任何东西，所以您已经拥有它。