MVVM-C View(Controller)

CountryListViewController.swift

import Foundation
import UIKit

typealias CountryListViewModelProtocol = CountryListDatasource & ViewModel & Searchable

protocol CountryListDatasource {
    var screenTitle: String { get }
    var numberOfSections: Int { get }
    func numberOfRows(in section: Int) -> Int
    func itemForRow(at indexPath: IndexPath) -> CountryListItemRepresentable
    func country(at indexPath: IndexPath) -> Country?
}

protocol CountryListItemRepresentable {
    var name: String { get }
    var capital: String { get }
}

protocol CountryListViewControllerDelegate: class {
    func didSelect(country: Country, in viewController: UIViewController)
}

final class CountryListViewController: UIViewController, LoadingDisplayable {
    
    private enum Identifier {
        static let cell = "CellIdentifier"
    }
    
    let loadingViewController = LoadingViewController()
    weak var delegate: CountryListViewControllerDelegate?
    private var viewModel: CountryListViewModelProtocol!
    
    @IBOutlet private weak var tableView: UITableView!
    @IBOutlet private weak var searchBar: UISearchBar!
    
    // MARK: - View Lifecycle
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        assert(viewModel != nil, "ViewModel for CountryListViewController can not be nil")
        setupUI()
        reloadData()
    }
    
    // MARK: - Internal methods
    
    func configure(viewModel: CountryListViewModelProtocol) {
        self.viewModel = viewModel
        self.viewModel.didUpdate = reloadData
        self.viewModel.didChangeState = showLoadingIndicator
    }
    
    // MARK: - Private methods
    
    private func setupUI() {
        title = viewModel.screenTitle
        searchBar.becomeFirstResponder()
    }
    
    private func reloadData() -> Void {
        tableView.reloadData()
    }
    
    private func showLoadingIndicator(isLoading: Bool, loadingMessage: String?) {
        guard isLoading else {
            hideLoading()
            return
        }
        
        showLoading(with: loadingMessage)
    }
}

// MARK: - TableView methods

extension CountryListViewController: UITableViewDelegate, UITableViewDataSource {
    
    func numberOfSections(in tableView: UITableView) -> Int {
        viewModel.numberOfSections
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        viewModel.numberOfRows(in: section)
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: Identifier.cell, for: indexPath)
        cell.textLabel?.numberOfLines = 0
        cell.detailTextLabel?.numberOfLines = 0
        
        let countryListItemViewModel = viewModel.itemForRow(at: indexPath)
        cell.textLabel?.text = countryListItemViewModel.name
        cell.detailTextLabel?.text = countryListItemViewModel.capital
        
        return cell
    }
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        guard let country = viewModel.country(at: indexPath) else { return }
        
        delegate?.didSelect(country: country, in: self)
    }
    
}

extension CountryListViewController: UISearchBarDelegate {
    
    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
        searchBar.resignFirstResponder()
        
        guard let searchString = searchBar.text,
            !searchString.isEmpty else {
                return
        }
        
        viewModel.searchFor(keyword: searchString)
    }
    
}