Question

我正在尝试根据从一串数字解析的索引从数组中检索值。我坚持这个错误，这个论坛中其他类似问题的答案似乎是针对更高级的开发人员（这是我的第一个iOS应用程序）。

该应用程序最终将从网站查找天气报告（每个5位数的“MAFOR”分组），解析每个组并使用每个字符查找阵列中的风向，速度，预测期等值。

游乐场代码如下，感谢任何有关我出错的地方的帮助（寻找***）

//: Playground - noun: a place where people can play

import UIKit

var str = "Hello, playground"

// create array for Forecast Period
let forecastPeriodArray = ["Existing conditions at beginning","3 hours","6 hours","9 hours","12 hours","18 hours","24 hours","48 hours","72 hours","Occasionally"]

// create array for Wind Direction
let windDirectionArray = ["Calm","Northeast","East","Southeast","South","Southwest","West","Northwest","North","Variable"]

// create array for Wind Velocity
let windVelocityArray = ["0-10 knots","11-16 knots","17-21 knots","22-27 knots","28-33 knots","34-40 knots","41-47 knots","48-55 knots","56-63 knots","64-71 knots"]

// create array for Forecast Weather
let forecastWeatherArray = ["Moderate or good visibility (> 3 nm.","Risk of ice accumulation (temp 0C to -5C","Strong risk of ice accumulkation (air temp < -5C)","Mist (visibility 1/2 to 3 nm.)","Fog (visibility less than 1/2 nm.)","Drizzle","Rain","Snow, or rain and snow","Squally weather with or without showers","Thunderstorms"]


// retrieve full MAFOR line of several information groups (this will be pulled from a web site)
var myMaforLineString = "11747 19741 13757 19751 11730 19731 11730 13900 11630 13637"

// split into array components wherever " " is encountered
var myMaforArray = myMaforLineString.components(separatedBy: " ")

let count = myMaforArray.count
print("There are \(count) items in the array")

// Go through each group and parse out the needed digits
for maforGroup in myMaforArray {
    print("MAFOR group \(maforGroup)")

    // get Forecast Period
    var idx = maforGroup.index(maforGroup.startIndex, offsetBy: 1)
    var periodInt = maforGroup[idx]
    print("periodInt is \(periodInt)")

    // *** here is where I am stuck... trying to use the periodInt index value to retrieve the description from the ForecastPeriodArray
    var periodDescription = forecastPeriodArray(periodInt)
    print("Forecast period = (forecastPeriodArray(periodInt)")


    // get Wind Direction
    idx = maforGroup.index(maforGroup.startIndex, offsetBy: 2)
    var directionInt = maforGroup[idx]
    print("directionInt is \(directionInt)")

    // get Wind Velocity
    idx = maforGroup.index(maforGroup.startIndex, offsetBy: 3)
    var velocityInt = maforGroup[idx]
    print("velocityInt is \(velocityInt)")

    // get Weather Forecast
    idx = maforGroup.index(maforGroup.startIndex, offsetBy: 4)
    var weatherInt = maforGroup[idx]
    print("weatherInt is \(weatherInt)")

}

Answer 1

@shallowThought很接近。

您正尝试按索引访问数组，因此请使用array[index]表示法。但是你的索引必须是正确的类型。因此，forecastPeriodArray[periodInt]不起作用，因为periodInt不是名称所暗示的Int。目前它的类型Character没有多大意义。

您可能尝试实现的是将字符转换为整数并使用它来访问数组：

var periodInt = Int(String(maforGroup[idx]))!

当字符实际上不表示整数时，您可能希望为案例添加错误处理。

从数组中检索值 - 获取“无法调用非函数类型String的值”

1 个答案: