Ios Swift-将数组中的值转换为双精度或浮点值

我有一个数组，其中的值是字符串（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，以便将它们全部相加。如何在swift中执行此操作？

如果您确定所有数组都是字符串，则可以直接将字符串转换为float或double

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

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

---

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) }
    }
}

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

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

如果你有一个数组？其中需要将所有字符串从可选任意转换为双精度：

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 = ["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

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

---

Swift 5.1

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

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

如何使用示例

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)

---

我得到一个错误：

类型“AnyObject？”不符合协议“StringType”

此扩展用于字符串数组。你能编辑你的问题并添加原始的输入源代码吗？这很奇怪。我正在从parse下载数组，其中的所有对象都应该是字符串：

var newarray=[object.objectForKey（“times”）]

你需要转换为[String]@JaganrajPalanivel，更新为Swift 3.1，数组中的Any代替AnyObject

x.map{Double（$0）？0}

在展开时避免nil；）或者使用

compactMap