Swift - 将数组中的值转换为双精度或浮点数

问题描述

我有一个数组，其值为字符串（但所有的字符串都是1.0，2.0等等）。我正在尝试将这些字符串转换为双精度或浮点数，因此我可以将它们全部加在一起。如何在swift中执行此操作？

解决方案

更新： Xcode 8.3.2•Swift 3.1 / p>

 扩展集合其中Iterator.Element == String {
 var doubleArray：[Double] {
 return flatMap {Double（$ 0）} 
} 
 var floatArray：[Float] {
 return flatMap {Float（$ 0）} 
} 
} 
  

用法：

  let strNumbersArray = [1.5，2.3，3.7，4.5] // [1.5，2.3，3.7，4.5] 
 let doublesArray = strNumbersArray.doubleArray // [1.5,2.3,3.7,4.5] 
 let floatsArray = strNumbersArray.floatArray // [1.5,2.3,3.7,4.5] 
 let total = doublesArray.reduce（0，+）// 12 
 let average = total / Double（doublesArray.count）// 3 
  

如果你有一个数组的任何？您需要将所有字符串从Optional Any转换为Double：

 扩展集合其中Iterator.Element == Any？ {
 var doubleArrayFromStrings：[Double] {
 return flatMap {Double（$ 0 as？String ??）} 
} 
 var floatArrayFromStrings：[Float] {
 return flatMap {Float（$ 0 as？String ??）} 
} 
} 
  

用法：

  let strNumbersArray：[Any？] = [1.5，2.3，3.7 ，4.5，nil] // [{Some1.5}，{Some2.3}，{Some3.7}，{Some4.5}，nil] 
 let doublesArray = strNumbersArray。 doubleArrayFromStrings // [1.5,2.3,3.7,4.5] 
 let floatsArray = strNumbersArray.floatArrayFromStrings // [1.5,2.3,3.7,4.5] 
 let total = doublesArray.reduce（0，+）// 12 
 let average = total / Double（doublesArray.count）// 3 
  




I have an array with values which are strings (but all the strings are values like 1.0, 2.0, etc). I'm trying to convert those strings into doubles or floats so I can add them all together. How do I do this in swift?

解决方案

update: Xcode 8.3.2 • Swift 3.1

extension Collection where Iterator.Element == String {
    var doubleArray: [Double] {
        return flatMap{ Double($0) }
    }
    var floatArray: [Float] {
        return flatMap{ Float($0) }
    }
}

usage:

let strNumbersArray = ["1.5","2.3","3.7","4.5"]   // ["1.5", "2.3", "3.7", "4.5"]
let doublesArray = strNumbersArray.doubleArray    // [1.5, 2.3, 3.7, 4.5]
let floatsArray = strNumbersArray.floatArray      // [1.5, 2.3, 3.7, 4.5]
let total = doublesArray.reduce(0, +)     // 12
let average = total / Double(doublesArray.count)  // 3

If you have an Array of Any? where you need to convert all strings from Optional Any to Double:

extension Collection where Iterator.Element == Any? {
    var doubleArrayFromStrings: [Double] {
        return flatMap{ Double($0 as? String ?? "") }
    }
    var floatArrayFromStrings: [Float] {
        return flatMap{ Float($0 as? String ?? "") }
    }
}

usage:

let strNumbersArray:[Any?] = ["1.5","2.3","3.7","4.5", nil]   // [{Some "1.5"}, {Some "2.3"}, {Some "3.7"}, {Some "4.5"}, nil]
let doublesArray = strNumbersArray.doubleArrayFromStrings    // [1.5, 2.3, 3.7, 4.5]
let floatsArray = strNumbersArray.floatArrayFromStrings      // [1.5, 2.3, 3.7, 4.5]
let total = doublesArray.reduce(0, +)     // 12
let average = total / Double(doublesArray.count)  // 3

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