Swift string strip all characters but numbers and decimal point?

Question

I have this string:

Some text: $ 12.3 9

I want to get as a result: 12.39

I have found examples on how to keep only numbers, but here I am wanting to keep the decimal point "."

What's a good way to do this in Swift?

Answer 1

This should work (it's a general approach to filtering on a set of characters) :

[EDIT] simplified and adjusted to Swift3

[EDIT] adjusted to Swift4

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

If you need to ignore anything past the second decimal point add this :

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

Answer 2

Easiest and simplest reusable way: you can use this regex replacement option. This replaces all characters except 0 to 9 and dot (.) .

---

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")
}

Answer 3

One possible solution to the question follows below. If you're working with text fields and currency, however, I suggest you take a look at the thread Leo Dabus linked to.

extension String {
    func filterByString(myFilter: String) -> String {
        return String(self.characters.filter {
            myFilter.containsString(String($0))
            })
    }
}

var a = "$ 12.3 9"
let myFilter = "0123456789.$"
print(a.filterByString(myFilter)) // $12.39