Unable to convert String to double Swift

Question

For my app I need to convert a String to a double because I have to create a CLLocationObject for my App and therefore I need those doubles. Therefore I tried this:

 let lat = (cityObject.lat as! NSString).doubleValue

if I print the normal String I get the following:

some("Optional(52.523553)") some("Optional(13.403783)")

and if I print my double value, I get the following:

0.0 0.0

Could you try : Double(cityObject.lat as! NSString) or Double(cityObject.lat) ? — michael-martinez, Apr 17 '18 at 19:41
cityobject.lat is a string and i parse this value from Firebase — Dominik, Apr 17 '18 at 19:41
write it's first 2 charaters and look to the type in the autocomplete menu ,,, write **cityObject.la** — Shehata Gamal, Apr 17 '18 at 19:48

Jogendar Choudhary · Accepted Answer · 2018-04-18T05:16:16.663

3

Please try this:

extension String {
    func toDouble() -> Double? {
        return NumberFormatter().number(from: self)?.doubleValue
    }
}

You can access like that:

var myString = "1.2"
var myDouble = myString.toDouble()

You can remove optional as below:

if let data:NSDictionary = snap.value as! NSDictionary,  let lat = data.value(forKey: "lat"),let lng = data.value(forKey: "lng") {
    //then use thes let long to convert in Double

    let latValue = lat.toDouble()
    let lngValue = lng.toDouble()
    }

edited Apr 18 '18 at 05:16

answered Apr 17 '18 at 19:58

Jogendar Choudhary

3,476
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alue of type 'String' has no member 'toDouble' – Dominik Apr 17 '18 at 20:38
Can you explain it more? – Jogendar Choudhary Apr 17 '18 at 20:40
your code is working but my issue isnt fixed because i found out that i receive an Optional String from my Firebase Database and thats not working with your extension. Do you know how i can remove the Optional Extension? – Dominik Apr 17 '18 at 20:55
it would be great if you could check my code: https://stackoverflow.com/questions/49887481/how-to-remove-optional-from-string-value-swift – Dominik Apr 17 '18 at 21:08
@Dominik try `if let dict = snap.value as? [String: Any], let lat = dict["lat"] as? Double, let lng = dict["lng"] as? Double, let radius = dict["radius"] as? Double {` – Leo Dabus Apr 17 '18 at 23:10

score 1 · Answer 2 · answered Apr 17 '18 at 20:54

1

Double has a failable initializer that takes a String and returns an optional Double?, since obviously not all Strings are valid Doubles. That means you need to unwrap the result:

guard let value = Double("1.0") else {
   print("Not a valid Double")
}
print(value)

answered Apr 17 '18 at 20:54

Josh Homann

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Silly error: you missed a *scope exit* inside your `guard` (e.g., `return`, `thow`, etc). – Paulo Mattos Apr 18 '18 at 12:59

midhun p · Answer 3 · 2018-08-27T10:05:35.297

-1

please try below one, it will work perfectly

extension String {

var toDoubleVal: Double {

    return Double(self) ?? 0.0
}

}

edited Aug 27 '18 at 10:05

answered Aug 27 '18 at 05:30

midhun p

1,987
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Unable to convert String to double Swift

3 Answers3