Swift-将数组中的值转换为双精度或浮点型

Question

我有一个数组，其值是字符串（但所有字符串都是1.0、2.0等值）。我正在尝试将这些字符串转换为双精度或浮点型，以便可以将它们全部加在一起。如何迅速做到这一点？

Answer 1

更新：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) }
    }
}

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

如果您有任何数组？您需要将所有字符串从Optional Any转换为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 ?? "") }
    }
}

用法：

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

Answer 2

let x = ["1.0", "1.5", "2.0"]
print(x.map {Double($0)!})

Answer 3

如果您确定所有数组都是字符串，则可以将字符串直接转换为float或double。

let numberArray:Array = ["1.0","2.0","3.0"]
let stringFromArray = numberArray[0]
let floatFromString = Float(stringFromArray)
let doubleFromString = Double(stringFromArray)

Answer 4

Swift 5.1

extension Collection where Iterator.Element == String {
    var convertToDouble: [Double] {
        return compactMap{ Double($0) }
    }
    var convertToFloat: [Float] {
        return compactMap{ Float($0) }
    }
}

示例使用方法

let String_Array = ["1.5","2.3","3.7","4.5"]       // ["1.5", "2.3", "3.7", "4.5"]
let Double_Array = String_Array.convertToDouble    // [1.5, 2.3, 3.7, 4.5]
let Float_Array = String_Array.convertToFloat.     // [1.5, 2.3, 3.7, 4.5]

或您可以这样做

let numArray = ["1.0","2.0","3.0"]
let stringFromArray = numberArray[0]
let floatFromString = Float(stringFromArray)
let doubleFromString = Double(stringFromArray)