TableViewController.swift

//
//  TableViewController.swift
//  MultipleCollectionView
//
//  Created by Reo on 2019/11/08.
//  Copyright © 2019 uruly.xyz. All rights reserved.
//

// I partially copied the following code. 
// https://qiita.com/abouch/items/aca979b71ad792478687

import UIKit

struct Article: Codable {
    var title: String
    var user: User
    struct User: Codable {
        var id: String
    }
}

struct Qiita {

    static func fetchArticle(completion: @escaping ([Article]) -> Swift.Void) {

        let url = "https://qiita.com/api/v2/items"

        guard var urlComponents = URLComponents(string: url) else {
            return
        }

        urlComponents.queryItems = [
            URLQueryItem(name: "per_page", value: "50"),
        ]

        let task = URLSession.shared.dataTask(with: urlComponents.url!) { data, response, error in

            guard let jsonData = data else {
                return
            }

            do {
                let articles = try JSONDecoder().decode([Article].self, from: jsonData)
                completion(articles)
            } catch {
                print(error.localizedDescription)
            }
        }
        task.resume()
    }
}

final class TableViewController: UIViewController {

    @IBOutlet private weak var tableView: UITableView! {
        didSet {
            tableView.register(UITableViewCell.self, forCellReuseIdentifier: reuseIdentifier)
            tableView.delegate = self
            tableView.dataSource = self
        }
    }
    @IBOutlet weak var tableViewConstraintHeight: NSLayoutConstraint!

    private let reuseIdentifier = "cell"
    private var articles: [Article] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        Qiita.fetchArticle(completion: { [weak self] (articles) in
            self?.articles = articles
            DispatchQueue.main.async {
                self?.tableView.reloadData()
                // リロード後に高さを再設定してあげる！
                self?.updateTableViewHeight()
            }
        })
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        updateTableViewHeight()
    }

    private func updateTableViewHeight() {
        // Set tableView height to content size height.
        tableView.layoutIfNeeded()
        tableViewConstraintHeight.constant = tableView.contentSize.height
        view.layoutIfNeeded()
        view.frame.size.height = tableView.contentSize.height
    }
}

// MARK: - TableViewDelegate

extension TableViewController: UITableViewDelegate {}

// MARK: - UITableViewDataSource

extension TableViewController: UITableViewDataSource {

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return articles.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: reuseIdentifier, for: indexPath)
        cell.textLabel?.text = articles[indexPath.row].title
        return cell
    }
}