CODEWITHSUNDEEP
swiftswift3decimalnan
icekomo
icekomo

Reputation: 9466

trying to create a guard to check if an input comes back as NaN

I have an input field that allows user to input numbers( the string is converted to a decimal), but there is an occasion where they could be a $ an no number, in that case I would like to use a guard and pop up an UIAlert letting the user know of the mistake. I read that there is a BOOL property of isNaN for Decimal in Swift 3, but I'm not entirely sure how to use it. This is what I'm trying

guard myDecimalNumber != isNaN else {
        print("this is not a number show alert")
   }

Upvotes: 2

Views: 231

Answers (1)

Martin R
Martin R

Reputation: 539685

isNan is a boolean property of Decimal (and all floating point types), so you can check it with

guard !myDecimalNumber.isNaN else {
    // ... `myDecimalNumber` is NaN ...
}

But note that creating a Decimal from a string returns an optional which is nil if the conversion fails, so what you probably want is optional binding:

guard let myDecimalNumber = Decimal(string: textField.text) else {
    // ... `textField.text` does not represent a number ...
}

(and the same approach works for other number types like Double, Int, ...)

For proper handling of localized decimal separators, use a number formatter:

guard let myDecimalNumber = formatter.number(from: textField.text)?.decimalValue else {
    // ... `textField.text` does not represent a number ...
}

Upvotes: 3

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