Question

在编写Swift的UI来描述用户输入的信息并将信息写入数组时，“ getCommand（）”函数与“ readLine（）”一起使用！语句返回错误“线程1：致命错误：在展开可选值时意外发现nil”我不知道如何使用可选绑定对其进行修复。

import Foundation
    struct StatsVC {
        var data = [String : Stats]()
        var current = ""
        func getCommand() -> [String] {
            print("Command" , terminator : "...")
            return splitStrPar(readLine()!) //the troublemaker
        }
        mutating func runStats() {
            print("Hello, Welcome to the Krantz UI! Please enter your stats: ")
            var command = getCommand()
            var infoData: [Stats] = []
            while(command[0] != "quit") {
                switch command[0] {
                    case "current" : //code not important here, deleted other options for simplicity
                    default : print("I don't have that command in my system")
                }
                command = getCommand()
                if(command[0] == "quit") {
                    print("Krantz Laboratories Thanks You For a Productive Session")
                }
            }
        }
    }
//statsVC.swift
func splitStrPar(_ expression: String) -> [String]{
    return expression.split{$0 == " "}.map{ String($0) }
}
func splitStrLin(_ expression: String) -> [String]{
    return expression.split{$0 == "\n"}.map{ String($0) }
}
//stats.swift
import Foundation
struct Stats {
  var values: [Double]
  init(values: [Double]){
    self.values = values
  }
//other functions not important here
}
//main.swift
var vc = StatsVC()
vc.runStats()

Answer 1

将结构代码更改为以下内容，以正确处理可选包装。使用强制的可选包装后缀运算符!的做法不佳。我还自由地通过commands数组修改了迭代，以更好地完成我认为您想做的事情。

struct StatsVC {
    var data = [String : Stats]()
    var current = ""
    func getCommands() -> [String] {
        print("Command" , terminator : "...")
        guard let line = readLine() else { return [] }
        return splitStrPar(line)
    }
    mutating func runStats() {
        print("Hello, Welcome to the Krantz CLI! Please enter your stats: ")
        let commands = getCommands()
        var infoData: [Stats] = []
        for command in commands {
            switch command {
            case "current" :
                break //code not important here, deleted other options for simplicity
            case "quit":
                print("Krantz Laboratories Thanks You For a Productive Session")
                return
            default :
                print("I don't have that command in my system")
            }
        }
    }
}

可选错误：线程1：致命错误：展开可选值时意外发现nil

1 个答案: