Question

我想知道如何从弹出的ViewController传回数据

FirstViewController -----push----> SecondViewController

SecondViewController -----popped(Pass Value?) ----> FirstViewController

我已经四处寻找并找到了许多要求使用代表的解决方案，但那些是在我不熟悉的Objective C中。

我们如何在Swift中执行此操作？

谢谢

Answer 1

实际上代表不仅仅是目标C中的代表。在Swift中可以使用委托（任何不涉及Objective-C的动态特性的东西都可以在Swift中使用），委托是一种设计模式（delegation as a design pattern），不是语言实现。您可以使用两种方法之一，块/闭包或委派。可以在Apple的文档中找到swift委派的示例：

Apple documentation on delegation

您可能还会在此处看到有关闭包的Apple文档的参考资料： Apple documentation on closures

授权示例如下所示：

注意到委托是通过以下协议声明的：

protocol DiceGame {
    var dice: Dice { get }
    func play()
}
protocol DiceGameDelegate {
    func gameDidStart(game: DiceGame)
    func game(game: DiceGame, didStartNewTurnWithDiceRoll diceRoll: Int)
    func gameDidEnd(game: DiceGame)
}

该类检查它是否有委托，如果有，则调用类必须通过符合上述协议实现的方法

  class SnakesAndLadders: DiceGame {
        let finalSquare = 25
        let dice = Dice(sides: 6, generator: LinearCongruentialGenerator())
        var square = 0
        var board: [Int]
        init() {
            board = [Int](count: finalSquare + 1, repeatedValue: 0)
            board[03] = +08; board[06] = +11; board[09] = +09; board[10] = +02
            board[14] = -10; board[19] = -11; board[22] = -02; board[24] = -08
        }
        var delegate: DiceGameDelegate?
        func play() {
            square = 0
            delegate?.gameDidStart(self)//Calls the method gameDidEnd on the delegate passing self as a parameter
            gameLoop: while square != finalSquare {
                let diceRoll = dice.roll()
                delegate?.game(self, didStartNewTurnWithDiceRoll: diceRoll)
                switch square + diceRoll {
                case finalSquare:
                    break gameLoop
                case let newSquare where newSquare > finalSquare:
                    continue gameLoop
                default:
                    square += diceRoll
                    square += board[square]
                }
            }
            delegate?.gameDidEnd(self)//Calls the method gameDidEnd on the delegate passing self as a parameter
        }
    }

使用Swift从弹出的ViewController传回数据

1 个答案: