为什么我的代码会执行双重转场？

Question

我有一个视图控制器 subMenuViewController，它通过两个不同的 segue 链接，称为 DBSubLegislationSegue 和 TrafficSegue。

当用户从动态表中选择一个单元格时，代码应该检查选择了哪一行，并根据单元格执行正确的 segue 到新的 viewController。

当我运行代码时，应用程序总是在正确的视图控制器上结束，但是它通过执行两个 segue 来完成此操作，第一个 segue 始终是 Traffic Segue。

谁能帮助确定为什么要执行这种双重转场？

//populates the table with instances of SubMenuViewCell for each instance filling its label with the correct menuItems
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell =
    self.tableView.dequeueReusableCellWithIdentifier(
        "SubMenuCell", forIndexPath: indexPath)
        as! SubMenuTableViewCell

    let row = indexPath.row
    cell.subMenuLabel.font =
        UIFont.preferredFontForTextStyle(UIFontTextStyleHeadline)
    cell.subMenuLabel.text = subMenuItems[row]
    cell.accessoryType = UITableViewCellAccessoryType.DisclosureIndicator //adds disclosure arrow indicating further info to cell

    return cell
}

//function for handling when a table row is selected by the user.
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    //get the selected row index and save as rowSelected
    let myIndexPath = self.tableView.indexPathForSelectedRow()
    rowSelected = myIndexPath!.row
    println(rowSelected)
    if(rowSelected == 0){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 1){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 2){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 3){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 4){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 5){
       performSegueWithIdentifier("TrafficSegue", sender: nil)
    }
    if(rowSelected == 6){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 7){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 8){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 9){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 10){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }
    if(rowSelected == 11){
        performSegueWithIdentifier("DBSubLegislationSegue", sender: nil)
    }

 }

// MARK: - Navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    println(segue.identifier)
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 0 { //check the row and act appropriately
        let newViewController = segue.destinationViewController    //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "All Entries"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 1 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Common Law"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 2 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Police Procedure"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 3 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Police Powers"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 4 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Crime"
    }
    if segue.identifier == "TrafficSegue" && rowSelected == 5 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! TrafficSubMenuTableViewController
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 6 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "People"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 7 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Civil Order"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 8 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Sexual"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 9 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Licencing"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 10 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Firearms"
    }
    if segue.identifier == "DBSubLegislationSegue" && rowSelected == 11 { //check the row and act appropriately
        let newViewController = segue.destinationViewController     //set the new viewController(new page)
            as! LegislationDBQueryTableViewController
        newViewController.typeOfPage = "Terrorism"
    }

}

Answer 1

全部修复。

我的错误在于第一个 segue 我将动态 CELL 连接到下一个视图控制器，但是我的第二个 segue 从表视图本身连接到视图控制器。

通过确保两者都从表格视图本身连接，代码按预期工作。

Answer 2

您获得了双重转场，因为您通过在情节提要上拖动控件创建的转场会自动被调用。换句话说，既然你已经通过故事板创建了转场，就没有理由调用performSegueWithIdentifier。假设您已在情节提要中正确设置了标识符，那么您的其余代码将照常工作，因此您可以继续删除或注释掉 tableview.didSelectRowAtIndexPath 方法的内容。

我建议在准备 segue 时使用 else-ifs，例如：

if segue.identifier == "DBSubLegislationSegue" && rowSelected == 0 {
    //do things
}
else if segue.identifier == "DBSubLegislationSegue" && rowSelected == 1 {
    // do other things
}
//and so on