Unable to display the data into UICollection view-CodePudding

I am trying to display the data into UI collection view .I am following the MVVM Architecture pattern. I am following programatic approach . I put the break point , I can see onto console , The data is decoded from URL but problem is it not displaying the into view controller.

Here is the my network manager code .

import Foundation

protocol NetworkManagerProtocol{
    func getModel<T: Codable>(_ model: T.Type, from url: String, completion: @escaping (Result<T, NetworkError>) -> Void)
    func getData(from url: String, completion: @escaping (Result<Data, NetworkError>) -> Void)
  
}
class NetworkManager:  NetworkManagerProtocol{
    
    func getModel<T: Codable>(_ model: T.Type, from url: String, completion: @escaping (Result<T, NetworkError>) -> Void) {
        
        guard let url = URL(string: url) else {
            completion(.failure(.badURL))
            return
        }
        
        URLSession.shared.dataTask(with: url) { data, response, error in
            if let data = data {
                do {
                    let response = try JSONDecoder().decode(model, from: data)
                    completion(.success(response))
                } catch let error {
                    completion(.failure(.other(error)))
                }
            }
            
            if let error = error {
                completion(.failure(.other(error)))
            }
        }
        .resume()
        
    }
    
    func getData(from url: String, completion: @escaping (Result<Data, NetworkError>) -> Void) {
        guard let url = URL(string: url) else {
            completion(.failure(.badURL))
            return
        }
        
        URLSession.shared.dataTask(with: url) { data, response, error in
            if let data = data {
                completion(.success(data))
            }
            
            if let error = error {
                completion(.failure(.other(error)))
            }
        }
        .resume()
    }
}

Here is the View Model code.

import Foundation

class PhotoViewModel {
    
    
   private let networkManager: NetworkManagerProtocol
    
   
    var  hits = [Hit]()
    private var cache = [String: Data]()
    
    private weak var delegate: PhotoViewable?
    
    
    init(networkManager: NetworkManagerProtocol) {
        self.networkManager = networkManager
       
    }
    
    var rows: Int {
        return hits.count
    }
    
    func fecthPhotoRecord(){
        
        let networkUrl = NetworkURLs.baseURL
        networkManager.getModel(Photo.self, from: networkUrl) { [weak self] result in
            switch result{
            case.success(let photo):
                self?.hits = photo.hits
                self?.delegate?.refreshUI()
            case.failure(let error):
                print(error)
               self?.delegate?.showError()
            }
        
        }
    }
    func downloadImage(row: Int, completion: @escaping (Data) -> Void) {
        
        let hit = hits[row]
        let hitpath = hit.previewURL
        
        if let data = cache[hitpath] {
            completion(data)
            return
        }
        
        networkManager
            .getData(from: hitpath) { result in
                switch result {
                case .success(let data):
                    self.cache[hitpath] = data
                    DispatchQueue.main.async {
                        completion(data)
                    }
                case .failure(let error):
                    print(error)
                }
            }
    }
    
    
}

Here is the collection view cell ..

import UIKit

protocol ReusableView: AnyObject {
    static var identifier: String { get }
}
class PhotoCollectionViewCell: UICollectionViewCell {
    
    private lazy var imageView: UIImageView = {
        let imageView = UIImageView()
        imageView.frame = CGRect(x:0, y:0, width:50, height:50)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        return imageView
    }()
    
   private lazy  var tagLabel:UILabel = {
        let label = UILabel()
        label.font = UIFont.boldSystemFont(ofSize: 15)
        label.textColor = .black
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()
    
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        imageView.translatesAutoresizingMaskIntoConstraints = false
        self.contentView.addSubview(tagLabel)
            self.contentView.addSubview(imageView)
            NSLayoutConstraint.activate([
                
                tagLabel.topAnchor.constraint(equalTo: self.contentView.topAnchor),
                tagLabel.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor),
                tagLabel.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor),
                tagLabel.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor),
        
                imageView.topAnchor.constraint(equalTo: self.tagLabel.topAnchor),
                imageView.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor),
                imageView.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor),
            ])
           
            self.contentView.backgroundColor = .lightGray
    }
    func configureCell(tagName: String) {
        tagLabel.text = tagName
      
        
        }
    func configureImageCell(row: Int, viewModel: PhotoViewModel) {
        
        imageView.image = nil
        
        viewModel
            .downloadImage(row: row) { [weak self] data in
                let image = UIImage(data: data)
                self?.imageView.image = image
            }
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    
}
extension PhotoCollectionViewCell: ReusableView {
    static var identifier: String {
        return String(describing: self)
    }
}

Here is the code for view controller .

import UIKit

protocol PhotoViewable: AnyObject {
    func refreshUI()
    func showError()
}

class PhotoViewController: UIViewController {

    var viewModel : PhotoViewModel
    
    init(viewModel : PhotoViewModel) {
        self.viewModel = viewModel
        super.init(nibName: nil, bundle: nil)
    }
    
    private let collectionView: UICollectionView = {
           let viewLayout = UICollectionViewFlowLayout()
           let collectionView = UICollectionView(frame: .zero, collectionViewLayout: viewLayout)
           collectionView.backgroundColor = .white
           return collectionView
       }()
    
    private enum LayoutConstant {
           static let spacing: CGFloat = 16.0
           static let itemHeight: CGFloat = 300.0
       }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private var activityIndicator: UIActivityIndicatorView = {
       let activityIndicator = UIActivityIndicatorView()
       activityIndicator.translatesAutoresizingMaskIntoConstraints = false
       return activityIndicator
   }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupViews()
        setupLayouts()
        viewModel.fecthPhotoRecord()
        
        collectionView.delegate = self
        collectionView.dataSource = self
        view.backgroundColor = .lightGray
        collectionView.reloadData()
      

    }
    
    private func setupViews() {
            view.backgroundColor = .white
            view.addSubview(collectionView)

            collectionView.dataSource = self
            collectionView.delegate = self
            collectionView.register(PhotoCollectionViewCell.self, forCellWithReuseIdentifier: PhotoCollectionViewCell.identifier)
        }
    private func setupLayouts() {
           collectionView.translatesAutoresizingMaskIntoConstraints = false

           // Layout constraints for `collectionView`
           NSLayoutConstraint.activate([
               collectionView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
               collectionView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
               collectionView.leftAnchor.constraint(equalTo: view.leftAnchor),
               collectionView.rightAnchor.constraint(equalTo: view.rightAnchor)
           ])
       }
    
}

extension PhotoViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return viewModel.hits.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PhotoCollectionViewCell.identifier, for: indexPath) as! PhotoCollectionViewCell
        
        let row = indexPath.row
        let hits  = viewModel.hits[indexPath.row]
        cell.configureCell(tagName: hits.tags)
        cell.configureImageCell(row: row, viewModel: viewModel)
        
        return cell
    }
}

extension PhotoViewController: UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        let width = itemWidth(for: view.frame.width, spacing: LayoutConstant.spacing)

        return CGSize(width: width, height: LayoutConstant.itemHeight)
    }

    func itemWidth(for width: CGFloat, spacing: CGFloat) -> CGFloat {
        let itemsInRow: CGFloat = 2

        let totalSpacing: CGFloat = 2 * spacing   (itemsInRow - 1) * spacing
        let finalWidth = (width - totalSpacing) / itemsInRow

        return floor(finalWidth)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: LayoutConstant.spacing, left: LayoutConstant.spacing, bottom: LayoutConstant.spacing, right: LayoutConstant.spacing)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return LayoutConstant.spacing
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return LayoutConstant.spacing
    }
}

extension PhotoViewController: PhotoViewable {
    func refreshUI() {
        DispatchQueue.main.async {
           self.collectionView.isHidden = false
           // self.activityIndicator.stopAnimating()
            self.collectionView.reloadData()
        }
    }
    
    func showError() {
        DispatchQueue.main.async {
           // self.activityIndicator.stopAnimating()
            self.collectionView.reloadData()
        }
    }
}

Here is the console .

Here is the result of the screenshot.

CodePudding user response：

The problem is you are not setting the delegate for viewModel add the following line in viewDidLoad before calling viewModel.fecthPhotoRecord()

viewModel.delegate = self

CodePudding user response：

main problem is you didn't call the delegate for your viewModel before fetching the data, always setup you delegate before any data management in viewDidLoad

viewModel.delegate = self
viewModel.datasource = self //if needed datasource