UITextField's numerical pad: dot instead of comma for float values
Swift 4
extension String {
static let numberFormatter = NumberFormatter()
var doubleValue: Double {
String.numberFormatter.decimalSeparator = "."
if let result = String.numberFormatter.number(from: self) {
return result.doubleValue
} else {
String.numberFormatter.decimalSeparator = ","
if let result = String.numberFormatter.number(from: self) {
return result.doubleValue
}
}
return 0
}
}
"2.25".doubleValue // 2.25
"2,25".doubleValue // 2.25
Localized approach using NumberFormatter:
extension NumberFormatter {
static let shared = NumberFormatter()
}
extension StringProtocol {
var doubleValue: Double? {
return NumberFormatter.shared.number(from: String(self))?.doubleValue
}
}
Playground testing
// User device's default settings for current locale (en_US)
NumberFormatter.shared.locale // en_US (current)
NumberFormatter.shared.numberStyle // none
NumberFormatter.shared.decimalSeparator // "."
"2.7".doubleValue // 2.7
"2,7".doubleValue // nil
"$2.70".doubleValue // nil
NumberFormatter.shared.numberStyle = .currency
"2.7".doubleValue // nil
"2,7".doubleValue // nil
"$2.70".doubleValue // 2.7
NumberFormatter.shared.locale = Locale(identifier: "pt_BR") // pt_BR (fixed)
"2.7".doubleValue // nil
"2,7".doubleValue // nil
"R$2,70".doubleValue // 2.7
NumberFormatter.shared.numberStyle = .none
"2.7".doubleValue // nil
"2,7".doubleValue // 2.7
"R$2,70".doubleValue // nil
Potential duplicate of the SO Answer, use NSNumberFormatter
Example Swift:
let number = NSNumberFormatter().numberFromString(numberString)
if let number = number {
let floatValue = Float(number)
}
Example (Objective-C):
NSNumber *number = [[NSNumberFormatter new] numberFromString: numberString];
float floatValue = number.floatValue;
Nobody has really addressed the issue directly.
That is, the decimal separator is a convention for a locale.
iOS supports formatting numbers based on a particular locale.
If you're working purely in a given locale, then everything should work correctly. The keypad should accept numbers with the correct decimal separator.
If you're in most countries in Europe, for example, you'd enter a comma as the decimal separator. Entering a dot in those countries is wrong. Somebody from one of those countries would not do that, because it is the wrong decimal separator. A European user is going to know to use a comma as the decimal separator and you don't have to do anything.
If you are in the US, you'd use a period. Using a comma in the US would be wrong.
The way you should display a decimal number is with a number formatter. When you create a number formatter, it uses the current locale by default.
If you need to convert a string containing a decimal number from one locale to the other, you should use 2 number formatters. Use a formatter in the source locale to convert the string to a float. Then use a formatter with the destination locale to convert the number to a string in the output format.
Simply create one number formatter in the default current locale, and create a second number formatter and set it's locale explicitly to the other locale that you want to use.