View Controller Containment Injecting Empty Views

gistfile1.txt

//: Playground - noun: a place where people can play

import UIKit
import PlaygroundSupport

typealias JSONDictionary = [String:Any]

struct Resource<T> {
    
    let url :URL
    var parse :(Data) -> T?
}

struct Pokemon {
    
    var name :String
}

extension Pokemon {
    
    init?(dictionary :JSONDictionary) {
        
        guard let name = dictionary["name"] as? String else {
            fatalError("name not found")
        }
        
        self.name = name
    }
    
}

class WebService {
    
    func load<T>(resource :Resource<T>, completion:@escaping (T?) -> ()) {
        
        URLSession.shared.dataTask(with: resource.url) { (data, _, _) in
            
            DispatchQueue.main.async {
                 completion(resource.parse(data!))
            }
            
        }.resume()
    }
}

let pokemonURL = URL(string: "https://still-wave-26435.herokuapp.com/pokemon/all")!

let pokemonResource = Resource<[Pokemon]>(url: pokemonURL) {  result in
    
    let json = try! JSONSerialization.jsonObject(with: result, options: [])
    let dictionaries = json as! [JSONDictionary]
    return dictionaries.flatMap(Pokemon.init)
}

WebService().load(resource: pokemonResource) { pokemons in
    print(pokemons!)
}

class EmptyViewController : UIViewController {
    
    var message :String!
    
    init(message :String) {
        
        super.init(nibName: nil, bundle: nil)
        self.message = message
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.view.backgroundColor = UIColor.green
        
        let messageLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 300, height: 44))
        messageLabel.text = self.message
        self.view.addSubview(messageLabel)
    }
    
}

class EmptyView : UIView {
    
    init(delegate :UIViewController, message :String) {
        
        super.init(frame: delegate.view.frame)
        
        self.backgroundColor = UIColor.purple
        
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: 300, height: 44))
        label.textColor = UIColor.white
        label.text = message
        
        self.addSubview(label)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
}

class PokemonTableViewController : UITableViewController {
    
    var pokemons :[Pokemon]!
    
    init() {
        
        super.init(nibName: nil, bundle: nil)
        self.pokemons = [Pokemon]()
        populatePokemons()
    }
    
    private func populatePokemons() {
        
        WebService().load(resource: pokemonResource) { pokemons in
            
            if let pokemons = pokemons {
                
                if pokemons.isEmpty {
                    
                    self.view = EmptyView(delegate :self, message :"No Pokemons Found!")
                }
            }
        }
        
    }
    
    init(pokemons :[Pokemon]) {
        
        super.init(nibName: nil, bundle: nil)
        self.pokemons = pokemons
    }
    
    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return self.pokemons.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
       
        let cell = UITableViewCell(style: .default, reuseIdentifier: "Cell")
        cell.textLabel?.text = self.pokemons[indexPath.row].name
        return cell
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = UIColor.white
    }
    
    
    
}

class ContainerViewController : UIViewController {
    
    init<T>(resource :Resource<T>, build:@escaping (T) -> UIViewController) {
        
        super.init(nibName: nil, bundle: nil)
        
        WebService().load(resource: resource) { result in
            
            let content = build(result!)
            self.add(content :content)
        }
    }
    
    private func add(content :UIViewController) {
        
        // Remove any existing child controllers.
        for child in childViewControllers {
            child.willMove(toParentViewController: nil)
            child.view.removeFromSuperview()
            child.removeFromParentViewController()
        }
        
        addChildViewController(content)
        
        content.view.frame = self.view.bounds
        content.view.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(content.view)
        
        content.view.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        content.view.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        content.view.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        content.view.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        
        content.didMove(toParentViewController: self)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
}

let containerVC = ContainerViewController(resource: pokemonResource) { pokemons in
    
    if pokemons.isEmpty {
        return EmptyViewController(message : "No Pokemons Found!")
        
    } else {
        return PokemonTableViewController(pokemons :pokemons)
    }
}

let pokemonTVC = PokemonTableViewController()

PlaygroundSupport.PlaygroundPage.current.liveView = containerVC
PlaygroundSupport.PlaygroundPage.current.needsIndefiniteExecution = true