如何将数据从 UITableViewCell 传递到继承 NSObject 的 class

Question

Im trying to implement MVVM and Im using ViewController to update the UI, and a view-model to create an object and then to store all the properties of that object locally(user-defaults), now I would like to pass the data from a UITableViewCell to that NSObject class and to store it inside the object property.

TableViewCell:

import UIKit

protocol AlbumsPickerCellDelegate {
    func didSelectedAlbum(_ selectedAlbum: String)
}



class AlbumsPickerTableViewCell: UITableViewCell {

//    var indexPath: IndexPath!

    @IBOutlet var albumsPicker: UIPickerView!
    

    
    var pickerData = ["Album1", "Album2", "Album3"]
    var albumsPickerCellDelegate:  AlbumsPickerCellDelegate?
    
    var isPickerDown = false
    
    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
        self.albumsPicker.delegate = self
        self.albumsPicker.dataSource = self
        
        
        albumsPicker.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            albumsPicker.topAnchor.constraint(equalTo: self.topAnchor),
            albumsPicker.bottomAnchor.constraint(equalTo: self.bottomAnchor),
            albumsPicker.leadingAnchor.constraint(equalTo: self.leadingAnchor),
            albumsPicker.trailingAnchor.constraint(equalTo: self.trailingAnchor),
//            albumsPicker.widthAnchor.constraint(equalToConstant: 100),
//            albumsPicker.heightAnchor.constraint(equalToConstant: 40),
            albumsPicker.heightAnchor.constraint(lessThanOrEqualToConstant: 140),
            albumsPicker.centerXAnchor.constraint(equalTo: self.centerXAnchor),
            albumsPicker.centerYAnchor.constraint(equalTo: self.centerYAnchor)


            
        ])
        
        
        self.preservesSuperviewLayoutMargins = false
        self.separatorInset = UIEdgeInsets(top: 0, left: 15, bottom: 0, right: 15)
        self.layoutMargins = UIEdgeInsets(top: 0, left: 15, bottom: 0, right: 15)
    }

    
    
//    class func cellHeight() -> CGFloat {
//        return 162.0
//    }
    
    
}

extension AlbumsPickerTableViewCell: UIPickerViewDelegate, UIPickerViewDataSource {
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1

    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return pickerData.count
    }
    
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return pickerData[row]
    }
    
    
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        isPickerDown = true
        
        let selectedAlbumOption = pickerData[row]
        
        if let delegate = albumsPickerCellDelegate {
            delegate.didSelectedAlbum(selectedAlbumOption)
        }
        
       

        
    }
    
    
    
    
}

ViewModel:

import Foundation
import UIKit


class FilterViewModel: NSObject, AlbumsPickerCellDelegate {
    
    var albumCell = AlbumsPickerTableViewCell()
    
    //Class vars:
    var selectedActivityByUser: String?
    var selectedPostTypesByUser: [String]?
    var selectedHashTagsByUser: [String]?
    var startDate: Date?
    var endDate: Date?
    var selectedAlbumByUser: String?
    
    //    var userFilter = FilterModel(byActivity: selectedActivityByUser, postType: selectedPostTypesByUser, hashTags: selectedHashTagsByUser, startDate: startDate, endDate: endDate, album: selectedAlbumByUser)
    
    override init() {
        super.init()
        //Sets the delegate as self:
        albumCell.albumsPickerCellDelegate = self
    }
}


//TODO: Pass all the info into FilterViewModel with delegates
extension FilterViewModel {
    
    func didSelectedAlbum(_ selectedAlbum: String) {
        self.selectedAlbumByUser = selectedAlbum
    }
}

Answer 1

A delegate from the view to the model is the wrong approach. It cannot work. There are multiple table view cells and the default initializer AlbumsPickerTableViewCell() creates another new instance of the cell which is never used in the table view.

The correct approach is a delegate (in Swift a callback closure is preferable) from the table view cell to the view controller passing the data and the index path. The controller updates the model at the given index (path).

---

In AlbumsPickerTableViewCell add a property callback

weak var callback : ((UITableViewCell, String) -> Void)?

And replace didSelectRow with

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    isPickerDown = true
    
    callback?(self, pickerData[row])        
}

In the view controller in cellForRow assign the closure to callback , replace datasource with the name of the real datasource array

cell.callback = { actualCell, album in 
    let actualIndexPath = tableView.indexPath(for: actualCell)!
    self.datasource[actualIndexPath.row].selectedAlbumByUser = album
}

Delete the entire code related to the protocol/delegate.

And there is no need that the model inherits from NSObject, not even it's supposed to be a class.