How to format a decimal number (double) to a string with a certain precision and based of the default Locale?

Question

So far I was formatting my doubles into Strings like this:

String(format:"%0.4f", rate)

Problem: the decimal separator is always . while in France for example we use ,

Then I used an NSNumberFormatter with numberStyle = .DecimalStyle but then I cannot choose the precision of 4 digits as I did before.

What are my solutions?

Thanks

NSNumberFormatter has many properties to control the output format. Did you try setting minimumFractionDigits/maximumFractionDigits ? — Martin R
– Martin R, Commented Mar 10, 2015 at 7:51
Yes it was actually what I was looking for and couldn't find the keyword "fraction". Thanks. — Nico
– Nico, Commented Mar 10, 2015 at 8:09

Martin R · Accepted Answer · 2017-10-24 08:44:47Z

8

Use a NSNumberFormatter and set both the minimum and maximum fraction digits to use:

let fmt = NSNumberFormatter()
fmt.maximumFractionDigits = 4
fmt.minimumFractionDigits = 4
let output = fmt.stringFromNumber(123.123456789)!
println(output) // 123,1235 (for the German locale)

Update for Swift 3 (and later):

let fmt = NumberFormatter()
fmt.maximumFractionDigits = 4
fmt.minimumFractionDigits = 4
let output = fmt.string(from: 123.123456789)!
print(output) // 123,1235 (for the German locale)

edited Oct 24, 2017 at 8:44

answered Mar 10, 2015 at 8:36

Martin R

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2 Comments

Johnny Over a year ago

NSNumberFormatter has renamed to NumberFormatter in swift 4

Martin R Over a year ago

@Johnny: You are right (and actually already in Swift 3), thanks for the notice!

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