swiftui函数显示“在视图更新期间修改状态”，这将导致不确定的行为。”

Question

该代码的作用是，它像我想要的那样提出了5个随机辅音和2个元音，但是它显示了一条警告消息，即“在视图更新过程中修改状态，这将导致不确定的行为”。

我是Swift的新手，当我搜索Swiftui和“在查看更新过程中修改状态，这将导致不确定的行为”时，我不理解我在线阅读的答案。至少我对修复自己的代码的理解不足。我无法弄清楚如何修改代码以摆脱警告。请帮忙。

仅供参考 - 我想将元音和辅音保留在（排序）阵列中，这些数组将在按下按钮滚动新的随机元音和辅音时进行更新。

import SwiftUI

struct ContentView: View {
  @State private var vowels = ["X","X"]
  @State private var consonants = ["X","X","X","X","X"]
  
  var body: some View {
    VStack {
      Spacer()
      Text(rollConsonants())
      Text(rollVowels())
      Spacer()
      Button("Reroll") {
        _ = rollVowels()
        _ = rollConsonants()
      }
    }
    .font(.largeTitle)
  }
  
  
  func rollVowels() -> String {
    vowels = ["A","E","I","O","U"].shuffled().prefix(2).sorted()   // message here
    let string = vowels.joined(separator:"   ")
    return string
  }
  
  func rollConsonants() -> String {
    let commonConsonants = ["C","D","L","N","R","S","T"].shuffled().prefix(2)
    var otherConsonants = ["B","F","G","H","K","M","P","V","W","Y","*"].shuffled().prefix(3)
    let rareConsonants = ["J","Q","X","Z"].shuffled()
    if let i = otherConsonants.firstIndex(of: "*") {
      otherConsonants[i] = rareConsonants[0]
    }
    consonants = (commonConsonants + otherConsonants).sorted()   // message here
    let string = consonants.joined(separator:"   ")
    return string
  }

  
}

Answer 1

这是因为：

Text(rollConsonants())
Text(rollVowels())

当Swiftui试图渲染文本时，您正在修改状态。

此更改可以通过从国家阅读行为中更新状态的行为来解决警告：

import SwiftUI

struct ContentView: View {
    @State private var vowels = ["X", "X"]
    @State private var consonants = ["X", "X", "X", "X", "X"]

    var formattedVowels: String {
        vowels.joined(separator: "   ")
    }

    var formattedConsonants: String {
        consonants.joined(separator: "   ")
    }

    var body: some View {
        VStack {
            Spacer()
            Text(formattedConsonants)
            Text(formattedVowels)
            Spacer()
            Button("Reroll") {
                rollVowels()
                rollConsonants()
            }
        }
        .font(.largeTitle)
    }

    func rollVowels() {
        vowels = ["A", "E", "I", "O", "U"].shuffled().prefix(2).sorted() // message here
    }

    func rollConsonants() {
        let commonConsonants = ["C", "D", "L", "N", "R", "S", "T"].shuffled().prefix(2)
        var otherConsonants = ["B", "F", "G", "H", "K", "M", "P", "V", "W", "Y", "*"].shuffled().prefix(3)
        let rareConsonants = ["J", "Q", "X", "Z"].shuffled()
        if let i = otherConsonants.firstIndex(of: "*") {
            otherConsonants[i] = rareConsonants[0]
        }
        consonants = (commonConsonants + otherConsonants).sorted() // message here
    }
}