以编程方式快速传递数据的问题
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【中文标题】以编程方式快速传递数据的问题【英文标题】：Issue With Passing Data Programmatically Swift 【发布时间】：2017-12-29 20:13:32 【问题描述】：我无法以编程方式将数据从一个 UICollectionViewController 传递到另一个 UICollectionViewController。
目前我的设置如下：
传递数据的 UICollectionViewController (RestaurantController)
1a。一个 UICollectionViewCell (RestaurantCell)
RestaurantCollectionViewCell)
正在接收数据的 UICollectionViewController (MenuController)
2a。一个 UICollectionViewCell (MenuCell)
在我的RestaurantCell 内部，我正在从 JSON 加载数据并将其附加到一个名为餐馆的新数组：var restaurants = [RestaurantModel]()。但是，当我尝试使用var restaurant: RestaurantModel? 在我的MenuController 中加载餐厅名称或任何餐厅对象时，我得到的值为零。我有一种感觉，要么我的设置不正确，要么我在某个地方犯了一个愚蠢的错误。也许两者兼而有之。我在下面为每个班级粘贴了我的代码。
在 MenuController 内返回 nil 的值：
print("Restaurant Name:", restaurant?.name)
print("Restaurant Id:", restaurant?.id)
自定义委派是否会导致问题？
非常感谢您的帮助和建议！
在我的RestaurantController里面：
import UIKit
import FBSDKLoginKit
class RestaurantController: UICollectionViewController, UICollectionViewDelegateFlowLayout, SWRevealViewControllerDelegate, UISearchBarDelegate, RestaurantDelegate
var restaurantCell: RestaurantCell?
private let restaurantCellId = "restaurantCellId"
override func viewDidLoad()
super.viewDidLoad()
collectionView?.backgroundColor = UIColor.qpizzaWhite()
collectionView?.register(RestaurantCell.self, forCellWithReuseIdentifier: restaurantCellId)
if self.revealViewController() != nil
navigationItem.leftBarButtonItem = UIBarButtonItem(image: #imageLiteral(resourceName: "icon_menu_24dp").withRenderingMode(.alwaysOriginal), style: .plain, target: self.revealViewController(), action: #selector(SWRevealViewController.revealToggle(_:)))
self.view.addGestureRecognizer(self.revealViewController().panGestureRecognizer())
// FIXME: issue with this...navigationcontroller is presenting, not pushing ontop of stack view
func didTapRestaurantCell(cell: RestaurantCell)
print("Did Tap Restaurant Cell - Restaurant Controller")
let layout = UICollectionViewFlowLayout()
let controller = MenuController(collectionViewLayout: layout)
navigationController?.pushViewController(controller, animated: true)
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: restaurantCellId, for: indexPath) as! RestaurantCell
cell.delegate = self
return cell
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
return 1
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
return CGSize(width: view.frame.width, height: view.frame.height)
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat
return 1
在我的RestaurantCell里面：
protocol RestaurantDelegate
func didTapRestaurantCell(cell: RestaurantCell)
class RestaurantCell: BaseCell, UISearchBarDelegate, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout
var delegate: RestaurantDelegate?
var restaurants = [RestaurantModel]()
var filteredRestaurants = [RestaurantModel]()
private let restaurantCollectionViewCell = "restaurantCollectionViewCell"
private let activityIndicator = UIActivityIndicatorView()
lazy var searchBar: UISearchBar =
let sb = UISearchBar()
sb.placeholder = "Search Restaurant"
sb.barTintColor = .white
UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self]).backgroundColor = UIColor.qpizzaWhite()
sb.delegate = self
return sb
()
lazy var collectionView: UICollectionView =
let layout = UICollectionViewFlowLayout()
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.backgroundColor = .white
return cv
()
override func setupViews()
super.setupViews()
collectionView.register(RestaurantCollectionViewCell.self, forCellWithReuseIdentifier: restaurantCollectionViewCell)
collectionView.delegate = self
collectionView.dataSource = self
backgroundColor = UIColor.qpizzaRed()
addSubview(searchBar)
addSubview(collectionView)
_ = searchBar.anchor(topAnchor, left: leftAnchor, bottom: nil, right: rightAnchor, topConstant: 4, leftConstant: 4, bottomConstant: 0, rightConstant: 4, widthConstant: 0, heightConstant: 50)
_ = collectionView.anchor(searchBar.bottomAnchor, left: leftAnchor, bottom: bottomAnchor, right: rightAnchor, topConstant: 0, leftConstant: 0, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)
loadRestaurants()
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String)
print(searchText)
filteredRestaurants = self.restaurants.filter( (restaruant: RestaurantModel) -> Bool in
return restaruant.name?.lowercased().range(of: searchText.lowercased()) != nil
)
self.collectionView.reloadData()
// MARK - Helper Methods
func loadRestaurants()
showActivityIndicator()
APIManager.shared.getRestaurants (json) in
if json != .null
// print("Restaurant JSON:", json)
self.restaurants = []
if let restaurantList = json["restaurants"].array
for item in restaurantList
let restaurant = RestaurantModel(json: item)
self.restaurants.append(restaurant)
self.collectionView.reloadData()
self.hideActivityIndicator()
else
print("Error loading JSON into Restaurant ViewController")
func loadImage(imageView: UIImageView, urlString: String)
let imageUrl: URL = URL(string: urlString)!
URLSession.shared.dataTask(with: imageUrl) (data, response, error) in
if let error = error
print("Error loading image for Restaurant Controller:", error.localizedDescription)
guard let data = data, error == nil else return
DispatchQueue.main.async(execute:
imageView.image = UIImage(data: data)
)
.resume()
func showActivityIndicator()
activityIndicator.frame = CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0)
activityIndicator.center = center
activityIndicator.hidesWhenStopped = true
activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.whiteLarge
activityIndicator.color = UIColor.qpizzaGold()
addSubview(activityIndicator)
activityIndicator.startAnimating()
func hideActivityIndicator()
activityIndicator.stopAnimating()
//MARK: CollectionView Delegate & DataSource Methods
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: restaurantCollectionViewCell, for: indexPath) as! RestaurantCollectionViewCell
let restaurant: RestaurantModel
if searchBar.text != ""
restaurant = filteredRestaurants[indexPath.item]
else
restaurant = restaurants[indexPath.item]
cell.restaurantNameLabel.text = restaurant.name
cell.restaurantAddressLabel.text = restaurant.address
if let logoName = restaurant.logo
let url = "\(logoName)"
loadImage(imageView: cell.restaurantLogoImageView, urlString: url)
return cell
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
if searchBar.text != ""
return self.filteredRestaurants.count
return self.restaurants.count
//FIXME: Restaurant Name Navigation Title is still not be passed from RestaurantCell to MenuController
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
print("Did Select Item - Restaurant Cell")
let layout = UICollectionViewFlowLayout()
let controller = MenuController(collectionViewLayout: layout)
controller.restaurant = self.restaurants[indexPath.item]
print("Controller", controller.restaurant) // Optional(QpizzaDelivery.RestaurantModel)
print("Restaurant:", self.restaurants) // [QpizzaDelivery.RestaurantModel, QpizzaDelivery.RestaurantModel, QpizzaDelivery.RestaurantModel]
print("IndexPath:", self.restaurants[indexPath.item]) // QpizzaDelivery.RestaurantModel
delegate?.didTapRestaurantCell(cell: self)
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
return CGSize(width: frame.width, height: 200)
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat
return 0.5
在我的MenuController里面：
import UIKit
class MenuController: UICollectionViewController, UICollectionViewDelegateFlowLayout, SWRevealViewControllerDelegate
private let menuCellId = "menuCellId"
var restaurant: RestaurantModel?
var menuItems = [MenuItemsModel]()
override func viewDidLoad()
super.viewDidLoad()
collectionView?.backgroundColor = UIColor.qpizzaWhite()
collectionView?.register(MenuCell.self, forCellWithReuseIdentifier: menuCellId)
collectionView?.alwaysBounceVertical = true
if self.revealViewController() != nil
navigationItem.leftBarButtonItem = UIBarButtonItem(image: #imageLiteral(resourceName: "menu2-black-32").withRenderingMode(.alwaysOriginal), style: .plain, target: self.revealViewController(), action: #selector(SWRevealViewController.revealToggle(_:)))
self.view.addGestureRecognizer(self.revealViewController().panGestureRecognizer())
print("Restaurant Name:", restaurant?.name) // returns nil
if let restaurantName = restaurant?.name
self.navigationItem.title = restaurantName
loadMenuItems()
func loadMenuItems()
print("Restaurant Id:", restaurant?.id) // returns nil
if let restaurantId = restaurant?.id
print("RestaurantId:", restaurantId)
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: menuCellId, for: indexPath) as! MenuCell
return cell
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
return 3
override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
let layout = UICollectionViewFlowLayout()
let controller = MenuDetailsController(collectionViewLayout: layout)
navigationController?.pushViewController(controller, animated: true)
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
return CGSize(width: view.frame.width, height: 120)
在我的MenuCell里面：
import UIKit
class MenuCell: BaseCell
let restaurantLabel: UILabel =
let label = UILabel()
label.text = "Restaurant King"
label.font = UIFont.boldSystemFont(ofSize: 16)
label.textColor = .black
label.numberOfLines = 0
return label
()
let mealImageView: UIImageView =
let iv = UIImageView()
iv.image = #imageLiteral(resourceName: "button_chicken").withRenderingMode(.alwaysOriginal)
iv.contentMode = .scaleAspectFill
iv.clipsToBounds = true
return iv
()
let mealDetailsLabel: UILabel =
let label = UILabel()
label.text = "Grass fed grass, American cheese, and friez"
label.font = UIFont.boldSystemFont(ofSize: 12)
label.textColor = UIColor.qpizzaBlack()
label.numberOfLines = 0
return label
()
let mealPriceLabel: UILabel =
let label = UILabel()
label.text = "$12.00"
label.font = UIFont.boldSystemFont(ofSize: 12)
label.textColor = UIColor.qpizzaBlack()
return label
()
let sepereatorView: UIView =
let view = UIView()
view.backgroundColor = UIColor.lightGray
return view
()
override func setupViews()
super.setupViews()
backgroundColor = UIColor.qpizzaWhite()
addSubview(restaurantLabel)
addSubview(mealImageView)
addSubview(mealDetailsLabel)
addSubview(mealPriceLabel)
addSubview(sepereatorView)
_ = mealImageView.anchor(topAnchor, left: nil, bottom: nil, right: rightAnchor, topConstant: 14, leftConstant: 0, bottomConstant: 0, rightConstant: 12, widthConstant: 60, heightConstant: 60)
_ = restaurantLabel.anchor(topAnchor, left: leftAnchor, bottom: nil, right: mealImageView.leftAnchor, topConstant: 14, leftConstant: 12, bottomConstant: 0, rightConstant: 10, widthConstant: 0, heightConstant: 20)
_ = mealDetailsLabel.anchor(restaurantLabel.bottomAnchor, left: leftAnchor, bottom: nil, right: mealImageView.leftAnchor, topConstant: 12, leftConstant: 12, bottomConstant: 0, rightConstant: 10, widthConstant: 0, heightConstant: 30)
_ = mealPriceLabel.anchor(mealDetailsLabel.bottomAnchor, left: leftAnchor, bottom: nil, right: rightAnchor, topConstant: 10, leftConstant: 12, bottomConstant: 10, rightConstant: 10, widthConstant: 0, heightConstant: 20)
_ = sepereatorView.anchor(nil, left: leftAnchor, bottom: bottomAnchor, right: rightAnchor, topConstant: 0, leftConstant: 20, bottomConstant: 4, rightConstant: 20, widthConstant: 0, heightConstant: 1)
【问题讨论】：
自从我弄乱了CollectionView以来已经有一段时间了，但是为什么didSelectItemAtIndexPath在单元格内而不是控制器内？您显然还创建了 2 个不同的 MenuController 实例，一个在单元格的 didSelectItemAtIndexPath 方法中，另一个在 RestaurantDelegate didTapRestaurantCell 方法中，它没有设置 restaurant 属性。在第一个中，您设置了餐厅，但该控制器实例只是停留了一段时间并且没有使用 - 它不是由导航控制器推动的。
didSelectItemAtIndexPath' is inside of RestaurantCell` 因为我在RestaurantCell 中有一个嵌套的 UICollectionViewController。您说我正在创建两个不同的MenuController 是正确的。我不知道如何在 RestaurantCell 中引用 MenuController 虽然没有创建新实例...您有什么提示吗？
我需要RestaurantController 中的第一个MenuController 实例将导航控制器推入堆栈，并需要RestaurantCell 中MenuController 的第二个实例以获取restaurant 的引用（其中引用我的餐厅模型）在我的MenuController
@a2b123 为什么要将单元格传回控制器类？为什么不直接将数据传回并segue 数据呢？您的协议应该包含餐厅类型的数据（这是您的模型数组），当您点击一个单元格时，您可以获得该单元格的数据，并提供给协议，它将委托给控制器类，然后您的 segue 将接受它到另一个班级。
@a2b123 我的意思是说委托部分，您将单元格传回，只需将点击的单元格数据传回，当调用返回到控制器类时，您可以将数据发送到第二类。
【参考方案1】：
快速浏览一下，声明一个正确类型的变量是开始。但是您实际上必须执行赋值 (=) 才能将数据或类引用从一个类移动到下一个类。
func didTapRestaurantCell(cell: RestaurantCell)
print("Did Tap Restaurant Cell - Restaurant Controller")
let layout = UICollectionViewFlowLayout()
let controller = MenuController(collectionViewLayout: layout)
navigationController?.pushViewController(controller, animated: true)
// you need to set the restaurant attribute of your new
// controller
let indexPath = indexPath(for: cell)
controller.restaurant = self.restaurants[indexPath.item]
【讨论】：
我如何在我的RestaurantController 中访问restaurants。我已经在RestaurantCell 中声明了该变量。另外，我如何在我的RestaurantController 中访问indexPath.item？ @ahalls。我尝试过多次使用该方法，但我只是不确定如何访问这些部分
这还不够，您必须将 Cell 映射到 restaurants 数组中的元素。
我看不到你一开始是如何填充单元格的？
func indexPath(for: UICollectionViewCell) Returns the index path of the specified cell.
对不起，我没有关注你的所有代码......但缺少的是创建后 MenuController 的属性值的实际分配 (=)。声明正确类型的属性是必要的第一步，接下来是对类的实际实例进行赋值【参考方案2】：
感谢所有评论并帮助我解决这个问题的人。我能够通过更改协议并将控制器作为参数传递来解决我的问题。
在RestaurantCell:
protocol RestaurantDelegate
func didTapRestaurantCell(cell: RestaurantCell, withMenuController: MenuController)
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)
print("Did Select Item - Restaurant Cell")
let layout = UICollectionViewFlowLayout()
let controller = MenuController(collectionViewLayout: layout)
controller.restaurant = self.restaurants[indexPath.item]
delegate?.didTapRestaurantCell(cell: self, withMenuController: controller)
在RestaurantController:
func didTapRestaurantCell(cell: RestaurantCell, withMenuController controller: MenuController)
print("Did Tap Restaurant Cell - Restaurant Controller")
navigationController?.pushViewController(controller, animated: true)
【讨论】：
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