ios - 向下滚动点击按钮继续下一个屏幕后如何验证 CustomCell 中的 UITextField - Swift 2.3

Question

我有一个动态表，在自定义单元格中包含多个UITextFields。但是，当我滚动到 TableView 底部并点击“继续”按钮时，我在获取 UITextFields 的 text 时遇到问题，滚动后退出屏幕。换句话说，我收到错误

fatal error :在解包可选值时意外发现 nil。

当我向下滚动到屏幕底部并点击继续按钮。

表格 View Controller :

class RNSContactInfoTableViewController: UITableViewController, UITextFieldDelegate, UITextViewDelegate {
    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

        if (indexPath.row == 0) {
            //static street address cell
            let streetAddressCell = tableView.dequeueReusableCellWithIdentifier("streetAddressCell", forIndexPath: indexPath) as! StreetAddressCell
            setStreetAddressTextFieldValue(streetAddressCell)
            return streetAddressCell
        } else if (indexPath.row == 1) {
            //static apt or suite cell
            let aptOrSuiteCell = tableView.dequeueReusableCellWithIdentifier("aptOrSuiteCell", forIndexPath: indexPath) as! AptOrSuiteCell
            setAptOrSuiteTextFieldValue(aptOrSuiteCell)
            return aptOrSuiteCell
        } else if (indexPath.row == 2) {
            //static city cell
            let cityCell = tableView.dequeueReusableCellWithIdentifier("cityCell", forIndexPath: indexPath) as! CityCell
            setCityTextFieldValue(cityCell)
            return cityCell
        } else if (indexPath.row == 3) {
            //static state cell
            let stateCell = tableView.dequeueReusableCellWithIdentifier("stateCell", forIndexPath: indexPath) as! StateCell
            setStateTextFieldValue(stateCell)
            return stateCell
        } else if (indexPath.row == 4) {
            //static zip code cell
            let zipcodeCell = tableView.dequeueReusableCellWithIdentifier("zipcodeCell", forIndexPath: indexPath) as! ZipCodeCell
            setZipcodeTextFieldValue(zipcodeCell)
            return zipcodeCell
        } else {
            //default cell
            let cell = UITableViewCell()
            return cell
        }
    }

    //--------------------------------------------------------
    // MARK: Button Tapped Methods
    //--------------------------------------------------------

    @IBAction func reviewServiceOrderButtonTapped(sender: UIButton) {

        //Dismiss keyboard when button is tapped
        self.view.endEditing(true)

        //Set user fields
        //<==========THE LINE BELOW IS CRASHING============>
        let streetAddressCell = self.tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 4, inSection: 0)) as! StreetAddressCell
        //<================================================>
        let streetAddressStr = streetAddressCell.streetAddressTextField.text

        let aptOrSuiteCell = self.tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 5, inSection: 0)) as! AptOrSuiteCell
        let aptOrSuiteStr = aptOrSuiteCell.aptOrSuiteTextField.text

        let cityCell = self.tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 6, inSection: 0)) as! CityCell
        let cityStr = cityCell.cityTextField.text

        let stateCell = self.tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 7, inSection: 0)) as! StateCell
        let stateStr = stateCell.stateTextField.text

        let zipcodeCell = self.tableView.cellForRowAtIndexPath(NSIndexPath(forRow: 8, inSection: 0)) as! ZipCodeCell
        let zipcodeStr = zipcodeCell.zipcodeTextField.text

        // Check for empty fields
        if (streetAddressStr!.isEmpty || cityStr!.isEmpty || stateStr!.isEmpty || zipcodeStr!.isEmpty || firstNameStr!.isEmpty || lastNameStr!.isEmpty || emailStr!.isEmpty || phoneAreaCodeStr!.isEmpty || phonePrefixStr!.isEmpty || phoneLineNumberStr!.isEmpty)
        {
            // Display error message
            self.displayAlertMessage(EMPTY_REQUIRED_FIELDS_ERROR_TITTLE, message: EMPTY_REQUIRED_FIELDS_ERROR_MESSAGE)
            return;
        }

    }
}

Answer 1

正如您所发现的，UITableView 所做的事情之一就是释放当前未显示的 UITableViewCell。这部分意味着 cellForRowAtIndexPath 将为当前不可见的单元格返回 nil。

您需要在单元格发生更改时以及在单元格滚出屏幕之前从单元格中提取数据(请参阅各种 UITextFieldDelegate 方法)，而不是稍后尝试查找单元格本身。

与这个特定问题无关，但还值得注意的是，当您上下滚动时，它将重用相同类型的单元格。