Swift字符串剥离所有字符但数字和小数点？

Question

我有这个字符串:

一些文字:12.3美元9

我希望得到结果:12.39

我找到了如何只保留数字的例子,但在这里我想保留小数点"."

在Swift中这样做的好方法是什么？

Answer 1

这应该工作(这是过滤一组字符的一般方法):

[编辑]简化并调整为Swift3

[编辑]调整为Swift4

let text     = "$ 123 . 34 .876"
let decimals = Set("0123456789.")
var filtered = String( text.filter{decimals.contains($0)} )

如果您需要忽略超过第二个小数点的任何内容,请添加:

filtered = filtered.components(separatedBy:".")    // separate on decimal point
                   .prefix(2)                      // only keep first two parts
                   .joined(separator:".")          // put parts back together

Answer 2

最简单和最简单的可重用方式：您可以使用此正则表达式替换选项。这将替换除 0 到 9 和点 (.) 之外的所有字符。

let yourString = "$123. 34"
//pattern says except digits and dot.
let pattern = "[^0-9.]"
do {
    let regex = try NSRegularExpression(pattern: pattern, options: NSRegularExpressionOptions.CaseInsensitive)

    //replace all not required characters with empty string ""
    let string_With_Just_Numbers_You_Need = regex.stringByReplacingMatchesInString(yourString, options: NSMatchingOptions.WithTransparentBounds, range: NSMakeRange(0, yourString.characters.count), withTemplate: "")

    //your number converted to Double
    let convertedToDouble = Double(string_With_Just_Numbers_You_Need)
} catch {
    print("Cant convert")
}