I need to convert a Double to String with a limit on max number of digits in Swift. I am using the following to limit the digits after decimal to 2.
numberString = String(format: "%.02f", 0.4394)
How to do something similar but limit the whole number to 5 digits i.e. 9438.45 to 9438.5
I would suggest using NumberFormatter and setting its maximumSignificantDigits property:
let fmt = NumberFormatter()
fmt.numberStyle = .decimal
//fmt.minimumSignificantDigits = 5 // optional depending on needs
fmt.maximumSignificantDigits = 5
var n = 0.43578912
for _ in 0..<5 {
print(fmt.string(for: n)!)
n *= 10
}
Output:
0.43579
4.3579
43.579
435.79
4,357.9
You can specify other formatting options as desired such as disabling the grouping separator.
Setting minimumSignificantDigits will be useful if you want trailing zeros with numbers that have fewer digits.
Use the "g" format specifier:
var n = 0.4354345
for i in 0..<5 {
print(String(format: "%5g", n))
n = n * 10
}
will give you:
0.435435
4.35435
43.5435
435.435
4354.35
Your next best option is going to be to convert and then fix up by truncating the string.
%5 results in 6 significant digits.
String(format:) function doesn't actually work like the c/c++ printf it mimics where a precision specifier on 'g' or 'G' specifies the number of significant digits to print.