Swift：通过单击按钮修改数据格式

Question

我的目标是使用一个按钮（包含多条消息）触发一个文本（制作标记，例如第一次单击将是方法1，第二次单击将是方法2）在末尾相应添加我的数据（加入后（分隔符：“~”）），这样当我回顾数据时，它可以帮助我分析点击了哪个按钮。

目前，我有一个可以输出数据的结构：

struct CaptureData {
var vertices: [SIMD3<Float>] //A vector of three scalar values. It will return a list of [SIMD3<Float>(x,y,z)]
var mode: Mode = .one
mutating func nextCase() { // the data method will be changed
    mode = mode.next()
}
var verticesFormatted : String {  //I formatted in such a way so that it can be read more clearly without SIMD3
let v = "<" + vertices.map{ "\($0.x):\($0.y):\($0.z)" }.joined(separator: "~") + "trial: \(mode.next().rawValue)"
        return "\(v)"
    }
}

基于@Joshua 的建议

enum Mode: String, CaseIterable {
    case one, two, three
}
extension CaseIterable where Self: Equatable {
    var allCases: AllCases { Self.allCases }
    var nextCase: Self {
        let index = allCases.index(after: allCases.firstIndex(of: self)!)
        guard index != allCases.endIndex else { return allCases.first! }
        return allCases[index]
    }
    @discardableResult
    func next() -> Self {
        return self.nextCase
    }
}

按钮在每次点击后交替显示消息，

  var x = 0
  var instance = CaptureData(vertices: [SIMD3<Float>])
// Next button for changing methods
@IBAction func ChangingTapped(_ btn: UIButton) {
  if(x==0){
      Textfield.text = "changing to driving"
  }
  else if(x==1){
       Textfield.text = "changing to walking"
     instance.nextCase()
  }
  else{
     Textfield.text = "changing to cycling"
     instance.nextCase()
  }
   x += 1
}

更新：我可以在分隔符“~”之后打印其中一种方法 .two（方法二）。但是，目前我仍然无法点击按钮切换数据中的大小写。

主要问题是变量的初始化。我无法定义var instance = CaptureData(vertices: [SIMD3<Float>])，因为它带有错误：Cannot convert value of type '[SIMD3<Float>].Type' to expected argument type '[SIMD3<Float>]'

如果我的解释有点混乱，我很抱歉。我试图描述我在这里遇到的问题。让我知道是否缺少任何东西！非常感谢您。

Answer 1

枚举是一种数据类型，它更像是一个常量，但可读性更高。

一个例子是将状态传递给一个函数。

enum Status {
   case success
   case failure
}

func updateStatus(_ status: Status) {
    statusProperty = status
}

// somewhere in your code
instance.updateStatus(.success)

相对于使用 Int 作为值。

func updateStatus(_ status: Int) {
    statusProperty = status
}

// somewhere in your code
instance.updateStatus(1) // eventually you'll forget what this and you'll declare more of a global variable acting as constant, which technically what enums are for.

swift 中的枚举有点不同，但功能更强大。有关枚举的更多信息here

回到主题。

enum Mode: String, CaseIterable {
    case one, two, three
}

extension CaseIterable where Self: Equatable {
    var allCases: AllCases { Self.allCases }
    var nextCase: Self {
        let index = allCases.index(after: allCases.firstIndex(of: self)!)
        guard index != allCases.endIndex else { return allCases.first! }
        return allCases[index]
    }

    @discardableResult
    func next() -> Self { // you don't need to update self here, remember self here is one of the items in the enum, i.e. one, so assigning one = two just doesn't work.
        return self.nextCase
    }
}

// The data struct
struct CaptureData {
    var mode: Mode = .one
   // we add a mutation function here so we can update the mode
    mutating func nextCase() { // the data your concern about, that can actually mutate is the mode property inside CaptureData struct. 
        mode = mode.next()
    }
}

所以让我们说在应用程序的某个地方，你可以像这样使用它，你初始化了一个 CaptureData 实例：

var instance = CaptureData() // Don't forget it should be var and not let, as we are updating its property.
instance.nextCase() // get the next case, initially it was .one
print(instance.mode) // prints two
instance.nextCase() // from .two, changes to .three
print(instance.mode) // prints three

希望这会有所帮助。