Swift|Swift 知识点1（#selector） Swift知识点1：#selector

2018年新的开始，好好的整理一下Swift知识点，希望在整理过程中提升自己。
1.swift 4.0 取消了 Selector("cyanButtonClick") 这种写法.

class ViewController: UIViewController {@IBOutlet weak var buttonA: UIButton!override func viewDidLoad() { super.viewDidLoad() //错误写法 buttonA.addTarget(self, action: Selector("buttonActionA"), for: .touchUpInside) //正确写法 buttonA.addTarget(self, action: NSSelectorFromString("buttonActionA"), for: .touchUpInside) }func buttonActionA(){ print("text for selector") } //以上写法已经被swift4.0取消，如果继续使用会被报“Use '#selector' instead of explicitly constructing a 'Selector' "

2.我们在开发过程中通常会这样写，坦率的讲这样写没什么问题，但是不够优雅

class ViewController: UIViewController { @IBOutlet weak var buttonA: UIButton! override func viewDidLoad() { super.viewDidLoad() //防止方法名重复，在方法前面跟上所在类以区别 buttonA.addTarget(self, action: #selector(ViewController.buttonActionA), for: .touchUpInside) }func buttonActionA(){ print("text for selector") }

3.如何访问我们的private私有方法，则是在前面加@Objc变成运行时。

class ViewController: UIViewController { @IBOutlet weak var buttonA: UIButton! override func viewDidLoad() { super.viewDidLoad() //当然如果不需要区分则可以去掉ViewController，也可以用self代替ViewController let methodObjc = #selector(ViewController.buttonActionObjc) buttonA.addTarget(self, action: methodObjc, for: .touchUpInside)}func buttonActionObjc(){ print("text for selectorObjc") }

4.相同方法名不同参数，可以用 as 区分

class ViewController: UIViewController { @IBOutlet weak var buttonA: UIButton! @IBOutlet weak var buttonB: UIButton! override func viewDidLoad() { super.viewDidLoad()let methodA = #selector(buttonActionA as () -> ()) let methodB = #selector(buttonActionB as (UIButton) -> ())buttonA.addTarget(self, action: methodA, for: .touchUpInside) buttonB.addTarget(self, action: methodB, for: .touchUpInside) }func buttonActionA(){ print("text for buttonActionA") }func buttonActionB(){ print("text for buttonActionB") }

5.Swift 3.0 中加入了 Selector 引用变量（不可为常量）的 getter 和 setter 方法：

相关链接：https://github.com/apple/swift-evolution/blob/master/proposals/0064-property-selectors.md 一直在找使用场景：a.可以判断属性是否包含getter 和 setter。b.可以结合responds方法使用。 class Person: NSObject { dynamic var firstName: String dynamic let lastName: String dynamic var fullName: String { return "\(firstName) \(lastName)" }init(firstName: String, lastName: String) { self.firstName = firstName self.lastName = lastName } } let firstNameGetter = #selector(getter: Person.firstName) let firstNameSetter = #selector(setter: Person.firstName)

【Swift|Swift 知识点1（#selector）】6.比较优雅的写法可以把Selector定义成extension，包含所有定义的selector

extension Selector {static let methodA = #selector(ViewController.buttonActionA)}class ViewController: UIViewController { @IBOutlet weak var buttonA: UIButton! override func viewDidLoad() { super.viewDidLoad()buttonA.addTarget(self, action: .methodA, for: .touchUpInside) }func buttonActionA(){ print("text for selector") }