# Discussion

## 目前正在做的作業

class ViewController: UIViewController {

    @IBOutlet weak var firstRoadLabel: UILabel!
    @IBOutlet weak var firstSpeedLimitLabel: UILabel!
    
    @IBOutlet weak var secondRoadLabel: UILabel!
    @IBOutlet weak var seconSpeedLimit: UILabel!
    
    @IBOutlet weak var thirdRoadLabel: UILabel!
    @IBOutlet weak var thirdSpeedLimit: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let task1 = DispatchQueue(label: "getFirstData")
        let task2 = DispatchQueue(label: "getSecondData")
        let task3 = DispatchQueue(label: "getThirdData")
        let group = DispatchGroup()
        group.enter()
        task1.async(group: group, qos: .default) { [self] in
            print("----task1 start----")
            getData(offset: "0")
            print("----task1 end----")
            group.leave()
        }
        group.wait()
        group.enter()
        task2.async(group: group, qos: .default) { [self] in
            print("----task2 start----")
            let data = getData(offset: "10")
            print("----task2 end----")
            group.leave()
        }
        group.wait()
        group.enter()
        task3.async(group: group, qos: .default) { [self] in
            print("----task3 start----")
            let data = getData(offset: "20")
            print("----task3 end----")
            group.leave()
        }
        
    }

    func getData(scope: String = "resourceAquire", rid: String = "5012e8ba-5ace-4821-8482-ee07c147fd0a", limit: String = "1", offset: String) {
        guard let url = URL(string: "https://data.taipei/opendata/datalist/apiAccess?scope=\(scope)&rid=\(rid)&limit=\(limit)&offset=\(offset)") else { return }
        var request = URLRequest(url: url)
        request.httpMethod = "Get"
        
        let session = URLSession(configuration: .default)
        
        let task = session.dataTask(with: request) {
            (data, response, error) in
            
            guard let response = response as? HTTPURLResponse, response.statusCode == 200, let data = data else { return }
            
            do {
                let dataResponse = try JSONDecoder().decode(Data.self, from: data)
                DispatchQueue.main.async { [self] in //這裡應該要改，但不確定要怎麼寫 
                    switch offset {
                    case "0":
                        configFirstLabels(dataResponse: dataResponse)
                    case "10":
                        configSecondLabels(dataResponse: dataResponse)
                    case "20":
                        configThirdLabels(dataResponse: dataResponse)
                    default:
                        print("This is the data you want: \(dataResponse)")
                    }
                }
            } catch {
                print(error)
            }
        }
        
        task.resume()
    }
    
    func configFirstLabels(dataResponse: Data) {
        firstRoadLabel.text = dataResponse.result.results.first?.設置路段
        firstSpeedLimitLabel.text = dataResponse.result.results.first?.速限
    }
    
    
}


struct Data: Codable {
    let result: DataResult
}

struct DataResult: Codable {
    let limit, offset: Int
    let results: [ResultElement]
}

struct ResultElement: Codable {
    let road, speedLimit: String

    enum CodingKeys: String, CodingKey {
        case road = "設置路段"
        case speedLimit = "速限"
    }
}

## 已解決
### 多個實體共用delegate

>extension ViewController: SelectionDataSource {
    func numberOfItems(_ selectionView: SelectionView) -> Int {
        方法一
        switch selectionView {
        case is topSelectionView:
            return topSource.count
        case is bottomSelectionView:
            return bottomSource.count
        default:
            return 0
        }
    }
    
>    func modelForItem(_ selectionView: SelectionView, at index: Int) -> ButtonModel {
        方法二
        switch selectionView.tag {
        case 0:
            return topSource[index]
        case 1:
            return bottomSource[index]
        default:
            return .init()
        }
    }
    
}

==A:「delegate方法要把自己傳進去」因為食物上就是會發生同一個人操作兩個同型別的實體 所以他故意把題目設計成上下兩個==
==A:你如果要辨認就是要仰賴這個實體是不是你所想的那一個==

### 回到流程首頁 v.s. 到tabbar的某頁

//回到流程首頁
@objc func goHomeVC(sender: UIButton) {
    self.navigationController?.popToRootViewController(animated: true)
    self.view.window?.rootViewController?.dismiss(animated: true, completion: nil) 
}

//到tabbar的某頁
@objc func goHomeVC(sender: UIButton) {
    self.tabBarController?.selectedIndex = 0 //push to homeVC
    self.navigationController?.popToRootViewController(animated: true) //when user selects cart of tabbar item, app shows cartVC
    self.view.window?.rootViewController?.dismiss(animated: true, completion: nil)
    }

### CoreData + Singletion design pattern
- `Singleton Design Pattern` 可以讓資料被app全域使用，但是只能透過一個入口取得（static宣告class實體/ private宣告取用入口實體 / private init初始化class實體）
- `CoreData` 封裝資料，可以新增.set / .insert、取得.retrieve、更新.update、刪除.delete
- key/value的形式存data
- `Notification Center`：物件可以去向通知中心註冊，成為某一種通知事件的觀察者，然後當有人向通知中心送出通知的時候，通知中心就會去找它的註冊表裡面，所有有註冊這個通知類型的觀察者，並將通知傳送給它們
- `Local SQLite Database`：`coreData`存放在local的位置

import CoreData

//設計模式1: 泛型工廠方法(靜態func產生實體)

class StorageManager {
    private let context = .......viewContext
    func create<T: NSManagedObject>(_ objType: T.Type) -> T {
        return T(context: context)
    }
}

// 如果用了設計模式1當你要建立物件要這樣做
let cartItem = StorageManager.shared.create(CartItem.self)
cartItem.size = "S"
cartItem.coloeCode = XXX
cartItrm.amout = 987654321

StorageManager.shared.save() // 這邊不知道你會怎麼寫


//設計模式2: Closure處理方法
class StorageManager {
    //裡頭包CoreData
    
    static let shared = StorageManager()
    private init() {} //prevent from creating another instance
    
    //connect StorageManager to AppDelegate
    private let appDelegate = UIApplication.shared.delegate as! AppDelegate
    //connect StorageManager to the context in AppDelegate
    private let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    
    func process(block: (_: NSManagedObjectContext) -> Void) {
        block(context)
        if context.hasChanges {
            try? context.save()
        }    
    }
}

// 如果用了設計模式2當你要建立物件要這樣做 (以insert為例)
StorageManager.shared.process { context in
    let cartItem = CartItem(context: context)
    cartItem.size = "S"
    cartItem.coloeCode = XXX
    cartItrm.amout = 987654321
}
//單用process closure，可以做的事情不侷限CRUD什麼都行，反正就是做完幫他呼叫一次save

### segue 替代方案
沒有StoryBoard，要怎麼做到以下的1-3行

let controller = GamesTableViewController()
controller.gamesArray = dataStore.allGames.summer

### 動畫由下而上升起

let xxxContraint = NSLayoutConstraint(item: <#T##Any#>, attribute: <#T##NSLayoutConstraint.Attribute#>, relatedBy: <#T##NSLayoutConstraint.Relation#>, toItem: <#T##Any?#>, attribute: <#T##NSLayoutConstraint.Attribute#>, multiplier: <#T##CGFloat#>, constant: <#T##CGFloat#>)
xxxContraint.constant = 20

UIView.animated {
    view.superview.layoutIfNeeded()
}
//更新的constraint要寫在動畫外面，讓他有時間去重新計算所有view 裡的constraints

### 建構

//建構物件時選擇使用哪個init，他就會從那個入口進來
//UIKit系列
override init(frame: CGRect) { // Designated
    super.init(frame: frame) //既然要覆寫又要建構 妳就會使用super呼叫自己父類別的建構
}

required init?(coder aDecoder: NSCoder) { // 不用SB就不用理他 或著 fatalError改super.init(coder: coder)
    fatalError("init(coder:) has not been implemented")
}

// 如果要自己帶東西進來
convenience init(color: UIColor) {
    self.init(frame: .zero) // 或是忽略.zero 因為frame的預設值就是.zero 所以就會寫成 self.init()
}


### 帶資料進新的view
1. 在AddToCartView寫一個公開func addProducts(_ products: [Product]) { //加入以後要做的事情 }
2.

let nextVC = DetailViewController()
nextVC.modalPrentationStyle = .選你想要的 ex.支付密碼是 .overCurrentContext/.overFullScreen
nextVC.products = products
present(nextVC, animated: true)


或者用convenience init的做法 就跟DetailViewController意思一樣
let nextVC = CartViewController(products: myPickedProducts)
nextVC.modalPrentationStyle = .overCurrentContext
present(nextVC, animated: true)

### 帶資料進新的VC
> 概念：寫一個自己想要的建構方法 依照你自己的喜好對VC初始化
補充：private是存取修飾 意味著我不想給class以外的任何人取用 所以當他要給的時候 只能透過我們寫的init

//原本的VC (HomeViewController) 的UITableViewDataSource裡，HomeVC打api拿到資料了
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let selectedProduct = hots[indexPath.section].products[indexPath.row]
    let detailVC = DetailViewController(product: selectedProduct) //product 只是argument label，可以任意取名字，只要後續在新的VC呼叫時用一樣的就好
    self.navigationController?.pushViewController(detailVC, animated:true)
}

//新的VC (DetailViewController)
class DetailViewController: UIViewController {
    convenience init(product: Product) { //product跟上述地方要用相同的argument label，另外Product是型別
        self.init()
        self.productData = product //有容器接住資料
    }
    
    private var productData: Product! //宣告容器
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        這邊就可以直接拿productData來用了，也可以塞到cell裡去了
        因為你在建構的時候把整個Product物件丟進來這個VC
        因為對於Home而言 selectedProduct不重要
        對DetailViewController才有意義
    }
}

//Usage:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let detailCell = tableView.dequeueReusableCell(withIdentifier: "\(DetailCell.self)", for: indexPath) as! DetailCell
    detailCell.detailLabel.text = productData.texture
}

### 怎麼做到點cell後換頁
`self.navigationController?.pushViewController(detailViewController, animated:true)`

### 切換tab後，回到最上方

//Class ViewController scope 有個按按鈕時會觸發的func，其中會清除producslist array
    func reset(selectedTab: Catalog) {
        self.selected = selectedTab
        productsPage = 0
        productManager.getProducts(selectedTab: selectedTab, page: productsPage!)
        productslist = []
        collectionView.es.resetNoMoreData()  
    }

extension CatalogViewController: ProductManagerDelegate {
    func manager(_ manager: ProductManager, didGet products: ProductData, selectedTab catalog: Catalog) {
        //判斷producslist array是不是空的，如果是的話代表是按完按鈕的情境
        let shouldScrollToTop = productslist.isEmpty
        productslist += products.data
        productsPage = products.nextPage
        collectionView.reloadData()
        //確定reload完data以後，讓畫面回到最上方（如果太早回最上方，會找不到collection view，會crash）
        if shouldScrollToTop {
            collectionView.setContentOffset(.zero, animated: true)
        }
    }
    
    func manager(_ manager: ProductManager, didFailWith error: Error) {
        print(error)
    }
}

### tableView和navigationbar沒有距離
safe area有關嗎？
==你的tableView沒有用Constraints-Layout，然後如果top想要接到navigationbar的bottom，妳可以接view.safeAreaLayoutGuide.topAnchor==
^^^^^ It works, thanks a loooooooot

-----------

### Anchor
啊我是覺得Anchor寫法跟snapkit比較像也比較短啦
貼一下Wii的大作

let stackView = UIStackView(arrangedSubviews: [textField, label])
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .horizontal
        stackView.distribution = .fillEqually
        stackView.alignment = .fill
        stackView.spacing = 4

        addSubview(stackView)
        
        label.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)

        NSLayoutConstraint.activate([
            stackView.leadingAnchor.constraint(equalTo: leadingAnchor),
            stackView.topAnchor.constraint(equalTo: topAnchor),
            stackView.bottomAnchor.constraint(equalTo: bottomAnchor),
            stackView.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -20)
        ])

// SnapKit 等效比對
addSubview(stackView)
stackView.snp.makeConstraints { make in
    make.leading.equalTo(self.snp.leading)
    make.top.equalTo(self.snp.top)
    make.bottom.equalTo(self.snp.bottom)
    make.trailing.equalTo(self.snp.trailing).offset(-20)
}

如果兩個Anchor是同一個邊，後面那一個可以不用寫
make.bottom.equalTo(self.snp.bottom)
相等於
make.bottom.equalTo(self)

另外因為此例中self即為superview
所以
make.bottom.equalTo(self)
可以寫成
make.bottom.equalToSuperview()

### 移除storyboard
設定：
1. https://medium.com/@Chien_Cheng/%E7%82%BA%E4%BB%80%E9%BA%BC%E4%B8%8D%E4%BD%BF%E7%94%A8-stordboard-813053e3692d
2. https://medium.com/swift-productions/ios-start-a-project-without-storyboard-xcode-12-253d785af5e7

var window: UIWindow?
    
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        
        // 俄羅斯娃娃
        let homeVC = HomeViewController()
        
        let homeNavC = UINavigationController(rootViewController: homeVC)
        homeNavC.navigationItem.titleView = UIImageView(image: UIImage(named: "Image_Logo02.png")!)
        homeNavC.tabBarItem = // 製作屬於他的 UITabBarItem
        
        let tabBarVC = UITabBarController()
        tabBarVC.setViewControllers([homeNavC, .init(), .init(), .init()], animated: false)
        
        window = UIWindow(frame: UIScreen.main.bounds)
        window!.backgroundColor = .white
        window!.makeKeyAndVisible()
        window!.rootViewController = tabBarVC
        
        return true
    }