ios - 展开 Segue 以保存到 Collection View 中

Question

我按照developer.apple.com上的教程在Xcode中使用表格 View 中的swift创建了一个菜谱应用程序。我已经开始转换为 Collection View ，但很难正确编码函数以展开和保存食谱的数据更改。

有人可以帮忙调整一下代码吗？目前，它不喜欢 selectedindexpath 的成员为 .row。已经有 saveMeals

的函数

错误

//MARK: Actions
@IBAction func unwindToMealList(sender: UIStoryboardSegue) {
    if let sourceViewController = sender.source as? MealViewController, let meal = sourceViewController.meal {
        
    if let selectedIndexPath =  collectionView.indexPathForSelectedRow {
        // Update an existing meal.
        meals[selectedIndexPath.row] = meal
        collectionView.reloadRows(at: [selectedIndexPath], with: .none)
    }
    else {
        // Add a new meal.
        let newIndexPath = IndexPath(row: meals.count, section: 0)
        
        meals.append(meal)
         collectionView.insertRows(at: [newIndexPath], with: .automatic)
    }
    // Save the meals.
    saveMeals()
    }
}
    

[在此处输入图像描述][2]

//MARK: Actions
    @IBAction func unwindToMealList(sender: UIStoryboardSegue) {
        if let sourceViewController = sender.source as? MealViewController, let meal = sourceViewController.meal {
            
            if let selectedIndexPath = collectionView?.numberOfSections{
                // Update an existing meal.
                meals[selectedIndexPath] = meal
                collectionView?.reloadData()
            }
            else {
                // Add a new meal.
                meals.append(meal)
                saveMeals()
                collectionView?.reloadData()

                       }
    }
    
    


}

这是餐课

import UIKit
import os.log

class Meal: NSObject, NSCoding {
    
    //MARK: Properties
    
    var name: String
    var photo: UIImage?
    var method: String?
    var ingredients: String?
    
    
    
    //MARK: Archiving Paths
    
    static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
    static let ArchiveURL = DocumentsDirectory.appendingPathComponent("meals")
    
    
    //MARK: Types
    
    struct PropertyKey {
        static let name = "name"
        static let photo = "photo"
        static let method = "method"
        static let ingredients = "ingredients"
        
        
    }
    
    //MARK: Initialization
    
    init?(name: String, photo: UIImage?, method: String?, ingredients: String?) {
        
        // The name must not be empty
        guard !name.isEmpty else {
            return nil
        }
        
        
        
        // Initialize stored properties.
        self.name = name
        self.photo = photo
        self.method = method
        self.ingredients = ingredients
        
        
    }
    
    //MARK: NSCoding
    func encode(with aCoder: NSCoder) {
        aCoder.encode(name, forKey: PropertyKey.name)
        aCoder.encode(photo, forKey: PropertyKey.photo)
        aCoder.encode(method, forKey: PropertyKey.method)
        aCoder.encode(ingredients, forKey: PropertyKey.ingredients)
        
    }
    
    required convenience init?(coder aDecoder: NSCoder) {
        
        // The name is required. If we cannot decode a name string, the initializer should fail.
        guard let name = aDecoder.decodeObject(forKey: PropertyKey.name) as? String else {
            os_log("Unable to decode the name for a Meal object.", log: OSLog.default, type: .debug)
            return nil
        }
        
        // Because photo is an optional property of Meal, just use conditional cast.
        let photo = aDecoder.decodeObject(forKey: PropertyKey.photo) as? UIImage
        
        let method = aDecoder.decodeObject(forKey: PropertyKey.method) as? String
        
        let ingredients = aDecoder.decodeObject(forKey: PropertyKey.ingredients) as? String
        
        
        
        // Must call designated initializer.
        self.init(name: name, photo: photo, method: method, ingredients: ingredients)
        
    }    }

导航

  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        super.prepare(for: segue, sender: sender)
        switch(segue.identifier ?? "") {
        case "AddItem":
            os_log("Adding a new meal.", log: OSLog.default, type: .debug)
        case "ShowDetail":
            guard let mealDetailViewController = segue.destination as? MealViewController else {
                fatalError("Unexpected destination: \(segue.destination)")
            }
            
            guard let selectedMealCell = sender as? MealCollectionViewCell else {
                fatalError("Unexpected sender: \(String(describing: sender))")
            }
            
            guard let indexPath = collectionView?.indexPath(for: selectedMealCell) else {
                fatalError("The selected cell is not being displayed by the table")
            }
            
            let selectedMeal = meals[indexPath.row]
            mealDetailViewController.meal = selectedMeal
            
            
        default:
            fatalError("Unexpected Segue Identifier; \(segue.identifier)")
            
        }

Answer 1

好吧，首先您需要了解这些 CollectionView 属性(如索引路径和内容)仅在 CollectionView 的委托(delegate)方法内部可用，而不能在其外部使用。

现在在您的代码中您可以这样做。添加部分很简单。只需添加 reloadData 调用

因此，您将膳食添加到数组列表中，然后调用上面的方法

meals.append(meal)
saveMeals()
collectionView.reloadData()

棘手的部分是如何编辑。因此，在编辑中，您可以做的是在您的展开 Segue 中获取餐食的值，您还需要获取已编辑的餐食的一些标识符，可能是餐食 ID 或其他内容。

然后在你的arrayList中你可以只编辑已经编辑过的id的Meal对象，然后保存它。然后调用collectionView.reloadData()。

或者您也可以在进行编辑时将索引路径从 itemSelected 传递到下一个 ViewController 并将其设置为属性。当您执行展开转场时，从 sourceViewController.selectedIndexPathProperty 等获取该属性，然后按照您目前使用的方式在此处使用它。