Swift

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数或浮点数，以便我可以将它们全部加在一起。我如何在 swift 中执行此操作？

Answer 1

let x = ["1.0", "1.5", "2.0"]
print(x.map {Double([=10=])!})

Answer 2

如果你确定你的所有数组都是字符串，你可以直接将你的字符串转换为 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 3

更新：Xcode 8.3.2 • Swift 3.1

extension Collection where Iterator.Element == String {
    var doubleArray: [Double] {
        return flatMap{ Double([=10=]) }
    }
    var floatArray: [Float] {
        return flatMap{ Float([=10=]) }
    }
}

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

如果你有任意数组？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([=12=] as? String ?? "") }
    }
    var floatArrayFromStrings: [Float] {
        return flatMap{ Float([=12=] 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 4

Swift 5.1

extension Collection where Iterator.Element == String {
    var convertToDouble: [Double] {
        return compactMap{ Double([=10=]) }
    }
    var convertToFloat: [Float] {
        return compactMap{ Float([=10=]) }
    }
}

示例如何使用

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]

或者你可以这样做

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

Swift - 将数组中的值转换为双精度数或浮点数

Swift - Convert values in array to doubles or floats

arrays

string

double

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