Swift. I pull out pictures in cells through api. Everything is being built, but instead of pictures it's empty. Returns nil. Explain please – Ios swift

I tried to make another version of your code and it’s able to run. You can check my code and compare with your own.

CoursesViewController

class CoursesViewController: UIViewController {
    private lazy var tableView: UITableView = {
        let tableView = UITableView(frame: .zero, style: .plain)
        tableView.translatesAutoresizingMaskIntoConstraints = false

        tableView.register(CourseCell.self, forCellReuseIdentifier: "CourseCell")

        tableView.delegate = self
        tableView.dataSource = self

        return tableView
    }()

    private var courses: [Course] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        setupViews()
        setupLayout()

        fetchCourses()
    }

    private func setupViews() {
        view.addSubview(tableView)
    }

    private func setupLayout() {
        tableView.snp.makeConstraints { make in
            make.edges.equalToSuperview()
        }
    }

    private func fetchCourses() {
        guard let url = URL(string: "https://swiftbook.ru//wp-content/uploads/api/api_courses") else {
            return
        }

        URLSession.shared.dataTask(with: url) { (data, _, _) in
            guard let data = data else {
                return
            }

            do {
                // получаем курсы в переменную
                self.courses = try JSONDecoder().decode([Course].self, from: data)
                // и мы должны перезагрузить таблицу
                DispatchQueue.main.async {
                    self.tableView.reloadData()
                }
            } catch let error {
                print(error)
            }
        }.resume()
    }
}

extension CoursesViewController: UITableViewDelegate, UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        courses.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        guard let cell = tableView.dequeueReusableCell(withIdentifier: "CourseCell", for: indexPath) as? CourseCell else {
            return UITableViewCell()
        }

        cell.configure(with: courses[indexPath.row])

        return cell
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        120
    }

    func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
        120
    }
}

Cell

class CourseCell: UITableViewCell {
    private lazy var nameLabel: UILabel = {
        let label = UILabel()

        label.numberOfLines = 0
        label.textColor = .black
        label.font = .systemFont(ofSize: 14, weight: .bold)

        return label
    }()

    private lazy var courseImage = UIImageView(frame: .zero)

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)

        setupViews()
        setupLayout()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func configure(with course: Course) {
        nameLabel.text = course.name

        DispatchQueue.global().async {
            guard let stringUrl = course.imageUrl,
                  let imageURL = URL(string: stringUrl),
                  let imageData = try? Data(contentsOf: imageURL)
            else {
                return
            }

            DispatchQueue.main.async {
                // Make sure it's the same course
                self.courseImage.image = UIImage(data: imageData)
            }
        }
    }

    private func setupViews() {
        courseImage.contentMode = .scaleAspectFill
        contentView.addSubview(nameLabel)
        contentView.addSubview(courseImage)
    }

    private func setupLayout() {
        nameLabel.snp.makeConstraints { make in
            make.top.leading.trailing.equalToSuperview().inset(8)
        }

        courseImage.snp.makeConstraints { make in
            make.centerX.equalToSuperview().inset(8)
            make.top.equalTo(nameLabel.snp.bottom).offset(12)
            make.height.width.equalTo(80)
        }
    }
}

• In my opinion, you should check your UI layout to make sure that the image view can be loaded and displayed properly.

Some Improvement suggestion

• Course.swift: Please use lower camel case convention for variables name because it’s the common Swift convention
• CourseCell.swift: Since the course don’t have ID so after a while you load image from background, this cell might be used by another because of the reuse cell mechanism.

DispatchQueue.main.async {
    // Make sure it's the same course
    if course.id == self.course.id {
        self.courseImage.image = UIImage(data: imageData)
    }
}

• Use caching mechanism every time you load image from the server so that next time you don’t need to fetch from the server again (you can set timeout for cache)
• Instead of handing loading image by yourself, you can use well-known 3rd party libs like SDWebImage or KingFisher.