如何使用 IndexPathsForSelectedRows？

Question

我正在尝试使用自定义方法（由另一个用户创建）复制我创建的称为 [Ingredient] 的结构的实例。方法是这样的；

convenience init(copyingIngredientsFrom meal: Meal, atIndexPaths indexPaths: [IndexPath]) {
        let sections = meal.ingredientSections
        self.init(mealTitle: selectedMeal!.mealTitle, mealID: selectedMeal!.mealID, mealImage: selectedMeal!.mealImage, ingredients: indexPaths.map {sections[$0.section][$0.row]})

最初的饭菜是；

 init(mealTitle: String, mealID: Int, mealImage: UIImage?, ingredients: [Ingredient]) {
        self.mealTitle = mealTitle
        self.mealID = mealID
        self.mealImage = mealImage!
        self.ingredients = [Ingredient]()
    }

新餐点旨在创建一个新的 [餐点] 对象，该对象复制所选成分。我在 IndexPathsForSelectedRows 使应用程序崩溃时遇到了一些问题。理想情况下，我还希望默认情况下“选择”行，但这不是必需的。可以看出，此代码在 segue 之前执行。理想情况下，一旦代码修复，我想追加 newMeal，而不是 SelectedMeal。这段代码的问题是它当前使应用程序崩溃，并且 indexPaths.count 仅在选择 1 和 x 之间的任何值时才显示 1 并且仍然崩溃，但如果我不选择任何值，则在单击后什么也不打印按钮。如果我删除 if 语句，那么应用程序可以正常工作，没有问题。

if let list = detailTableViewIn.indexPathsForSelectedRows {
                print(indexPaths.count)
                let newMeal = Meal(copyingIngredientsFrom: selectedMeal!, atIndexPaths: list)
            }

        myMeals.insert(selectedMeal!, at: myMealsPosition)

        myMealsPosition += 1

        // Segues away
        self.performSegue(withIdentifier: "MealCreated", sender: self)

任何帮助将不胜感激。

Answer 1

看这个例子：

  let Meals = [Meal]


    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

        performSegueWithIdentifier("MealCreated", sender: indexPath)
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
                let indexPath = self.tableView.indexPathForSelectedRow
                let meal = Meals[indexPath!.row]

                if segue.identifier == "MealCreated"{

                    let DetailMeal = (segue.destinationViewController as! DetailMealController)
                    DetailMeal.mealTitle = meal.mealTitle
                    DetailMeal.mealID = meal.mealID
                    DetailMeal.mealImage = meal.mealImage
                    DetailMeal.ingredients = meal.ingredients

                }
            }