ios - 委派为 nil ，MVVM 方法，两个 VC 具有相同的 VM。 iOS， swift

Question

有一个基类符合 ViewModelInsertProtocol 和函数 insertToCollection()。 delegate 在 CollectionViewController 类的 viewDidLoad 方法中设置为 self。

class CollectionViewController: UIViewController, ViewModelInsertProtocol {


func insertToCollection() {
    print("asdasd")
    collection.performBatchUpdates({
                     collection.insertItems(at: [IndexPath(row: viewModel.notes.count - 1, section: 0)])
                 }, completion: nil)
}


//MARK: -Variables

let reuseIdentifier = "cell"
var isEdit = false
var isSettingsEdit = false
var viewModel  = ViewModel()


//MARK: -OUTLETS

@IBOutlet var mainView: UIView!
@IBOutlet weak var bacgroundImageView: UIImageView!
@IBOutlet weak var collection: UICollectionView!
@IBOutlet weak var addButton: UIButton!
@IBOutlet weak var sideViewConstraint: NSLayoutConstraint!
@IBOutlet weak var settingConstraint: NSLayoutConstraint!
@IBOutlet weak var sideView: UIView!
@IBOutlet weak var icon: UIButton!
@IBOutlet weak var settingButton: UIButton!
@IBOutlet weak var backgr: UIButton!
//MARK: - LifeCycle

override func viewDidLoad() {
    super.viewDidLoad()


    configureUI()
    viewModel.delegate = self
 }

如果我想添加新的 UICollectionCell，我必须转到另一个 popVCPopVC 和我的基类有 viewModel 的实例

var View 模型 = View 模型()我对这两个类使用相同的 viewModel，看看 PopVC 中的 SaveBtn，在这个地方我使用委托(delegate)方法。

var viewModel = ViewModel()


//MARK: -Lifecycle

override func viewDidLoad() {
    super.viewDidLoad()

    configure()
    addObservers()
    viewModel.popDelegate = self


}
override func viewWillDisappear(_ animated: Bool) {
    viewModel.editSelected = false
}

func configure() {
    saveBtnOutlet.visualButton()
    xBtnOutlet.visualButton()
    cancelBtnOutlet.visualButton()
    firstCardColor.visualButton()
    secondCardColor.visualButton()

}


   @IBAction func CancelBtn(_ sender: Any) {
       dismiss(animated: true, completion: nil)
   }

   @IBAction func saveBtn(_ sender: Any) {

    viewModel.saveData(text: textF.text)
    dismiss(animated: true, completion: nil)

   }


rotocol ViewModelInsertProtocol: class {
func insertToCollection()
}

  extension ViewModel {

func numberOfRows() -> Int {
    return notes.count
}

}

class ViewModel {

var notes: Results<Model> {
    get{
        return realm.objects(Model.self)
    }
}
weak var delegate : ViewModelInsertProtocol? = nil
weak var popDelegate: PopDelegate? = nil
var backgroundImageIndex = 0
var editSelected = false
let realm = try! Realm()

var size = Sizes.largeSize
var background: String = "wood"

func saveData(text: String) {
    let newcard = Model()
    newcard.note = text
    RealmSerivce.shared.create(newcard)
    print(notes.count)
    if delegate == nil {print("nil")}
    delegate?.insertToCollection()

}

这段代码有什么问题？

Answer 1

按照 MVVM 方法和依赖注入(inject)，您可以注入(inject) ViewModel 而不是在弹出 Controller 中创建新实例，例如，如果您使用 Storyboard，则在准备 segue 时:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "PopVcIdentifier" {
        let popController = segue.destination as? PopVC
        popController?.viewModel = viewModel
    }
}

或者在 showPopUp 函数中:

func showPopUp() {
    let popController = PopVC()
    popController.viewModel = viewModel
    present(popController, animated: true)
}