Tip Trick IOS Swift.

self

• Golobal Func Global Func không thể sử dụng Self hoặc self.

func globalFunc (_ arg1: String) { 
    print(arg1) 
}

• Static/Class Func static và class truy cập thông qua class, không phải qua instance, self trong static và class là type, self trong instance chính là instance của object đó.

class Object {
    static func staticFunc() {
        print(self) // self trong static func là Type print: "Object"
    }
    
    class func classFunc() {
        print(self) // self trong class func là Type print: "Object"
    }
    
    func objectFunc() {
        print(self)// self trong object func là instance của Object
    }
}

Self

Self được sử dụng trong Protocol và trong Extension Protocol được dùng để ám chỉ loại adopt Protocol này.

extension MyProtocol {
    
    func protocolFunction()-> String {
        return "(Self.self)" // Self.self return về Type
    }
    
}

let object = MyClass()
object.protocolFunction() // "MyClass"

extension MyProtocol {
    
    static func staticProtocolFunction() {
        print(Self.self == self) // true // static func, self là Type,Self.self return Type -> true
    }
}

• có thể sử dụng Self để làm kết quả trả về.

protocol MyProtocol { 
    init () 
}
extension MyProtocol { 
    
    static func create () -> Self { 
        return Self () 
    }
}

Meta - Type

let type = MyViewController.self //get Type

• Bonus: Extension get Type trong các dự án mình hay sử dụng.

// MARK: - Response Type
protocol ResponseType {}

extension ResponseType {
    
    static var type: Self.Type {
        return Self.self
    }
    
    var type: Self.Type {
        return Self.self
    }
}

let vc = MyViewController()
let type = vc.type // return MyViewController.Type
let type = MyViewController.type // === MyViewController.self

• Get Tên Object

// MARK: - Response Identifier
protocol ResponseIdentifier {}

extension ResponseIdentifier {
    var identifier: String {
        return String(describing: type(of: self))
    }
    
    static var identifier: String {
        return String(describing: self)
    }
}

Ứng dụng

1. Get index của ViewController trong UINavigationController

extension UINavigationController {
    
    func index(of type: UIViewController.Type)-> Int? {
        return self.viewControllers.index(where: { vc in
            type(of: vc) == type
        })
    }
    
}
let navigationController = UINavigationController()
navigationController.index(of: MyViewController.type)

1. Response ObjectModel, Tạo Object Model kết hợp với Factory Methods

// MARK: - ResponseModel
protocol ResponseModel {
    init?(_ json: JSON?)
}

extension ResponseModel {
    
    static func responseObject(forKey: String? = nil, object: Any?) -> Self? {
        guard let object = object else {
            return nil
        }
        
        /// has key
        if let _forkey = forKey {
            let json = JSON(object)[_forkey]
            return self.init(json)
        }
        
        /// not key
        let json = JSON(object)
        return self.init(json)
    }
    
    static func responseCollectionObject(forKey: String? = nil, object: Any?) -> [Self]? {
        guard let object = object else {
            return nil
        }
        
        /// has key
        if let _forKey = forKey {
            let jsons = JSON(object)[_forKey].arrayValue
            return jsons.compactMap{self.init($0)}
        }
        
        /// not key
        let jsons = JSON(object).arrayValue
        return jsons.compactMap{self.init($0)}
    }
}

1. GetView trong file Nib

// MARK: - Response UIView
protocol ResponseUIView {}

extension ResponseUIView where Self: UIView {
    
    private static func fromNib<T: UIView>(_ type: T.Type) -> T? {
        if let view = Bundle.main.loadNibNamed(type.identifier, owner: nil, options: nil)?.first, let _view = view as? T {
            return _view
        } else {
            return nil
        }
    }
    
    static func fromNib() -> Self? {
        return fromNib(self)
    }
}

//example
let vc = MyViewController.fromNib()

1. Get ViewController trong file Storyboard

// MARK: - Response UIViewController
protocol ResponseUIViewController {}

extension ResponseUIViewController where Self: UIViewController {
    static func fromNib() -> Self {
        return self.init(nibName: String(describing: self), bundle: nil)
    }
    
    static func fromStoryboard(_ storyboardName: UIStoryboard.StoryboardName, withIdentifier: String = Self.identifier) -> Self? {
        return Self.fromStoryboard(self, storyboardName: storyboardName, withIdentifier: withIdentifier)
    }
    
    private static func fromStoryboard<T: UIViewController>(_ type: T.Type, storyboardName: UIStoryboard.StoryboardName, withIdentifier: String?) -> T? {
        let storyboard = UIStoryboard(storyboard: storyboardName, bundle: nil)
        return storyboard.instantiateViewController(type)
    }
}

1. Ứng dụng trong UITableView và UICollectionView

//====================== *** UITableView *** ======================
extension UITableViewCell {
    
    class var nib: UINib {
        return UINib(nibName: identifier, bundle: nil)
    }
    
    class var identifier: String {
        return String(describing: self)
    }
    
    class func dequeueCell(_ tableView: UITableView, indexPath: IndexPath) -> Self? {
        return tableView.dequeueCell(self, forIndexPath: indexPath)
    }
    
    class func dequeueCell(_ tableView: UITableView) -> Self? {
        return tableView.dequeueCell(self)
    }
}

extension UITableViewHeaderFooterView {
    class var nib: UINib {
        return UINib(nibName: identifier, bundle: nil)
    }
    
    class func dequeueHeaderFooter(_ tableView: UITableView) -> Self? {
        return tableView.dequeueHeaderFooter(self)
    }
}

extension UITableView {
    
    func registerCellByNib<T: UITableViewCell>(_ type: T.Type) {
        register(type.nib, forCellReuseIdentifier: type.identifier)
    }
    
    func registerCell<T: UITableViewCell>(_ type: T.Type) {
        register(type, forCellReuseIdentifier: type.identifier)
    }
    
    func registerHeaderFooter<T: UITableViewHeaderFooterView>(_ type: T.Type) {
        register(type.nib, forHeaderFooterViewReuseIdentifier: type.identifier)
    }
    
    func dequeueCell<T: UITableViewCell>(_ type: T.Type, forIndexPath indexPath: IndexPath) -> T? {
        return dequeueReusableCell(withIdentifier: type.identifier, for: indexPath) as? T
    }
    
    func dequeueCell<T: UITableViewCell>(_ type: T.Type) -> T? {
        return dequeueReusableCell(withIdentifier: type.identifier) as? T
    }
    
    func dequeueHeaderFooter<T: UITableViewHeaderFooterView>(_ type: T.Type) -> T? {
        return dequeueReusableHeaderFooterView(withIdentifier: type.identifier) as? T
    }
}

//====================== *** UICollectionView *** ======================
extension UICollectionViewCell {
    class var nib: UINib {
        return UINib(nibName: identifier, bundle: nil)
    }
    
    class var identifier: String {
        return String(describing: self)
    }
    
    class func dequeueCell(_ collectionView: UICollectionView, indexPath: IndexPath) -> Self? {
        return collectionView.dequeueCell(self, forIndexPath: indexPath)
    }
    
}

extension UICollectionView {
    func registerCellByNib<T: UICollectionViewCell>(_ type: T.Type) {
        register(type.nib, forCellWithReuseIdentifier: type.identifier)
    }
    
    func registerCell<T: UICollectionViewCell>(_ type: T.Type) {
        register(type, forCellWithReuseIdentifier: type.identifier)
    }
    
    func dequeueCell<T: UICollectionViewCell>(_ type: T.Type, forIndexPath indexPath: IndexPath) -> T? {
        return dequeueReusableCell(withReuseIdentifier: type.identifier, for: indexPath) as? T
    }
}