String formatting of a Double

Question

I can't seem to find a way to format a Double limiting the precision to just a couple of positions after the decimal point when presenting that in a label. Maybe I'm missing something major, but I couldn't find anything in the official documentation.

Thanks in advance for the help!

By the way, I would prefer `NSNumberFormatter`, which honors the device's `locale`. Thus `let formatter = NSNumberFormatter()`, set `minimumFractionDigits` and `maximumFractionDigits` to however many digits you want, and then you can do `let string = formatter.stringFromNumber(3.1415)`. — Rob, Mar 31 '15 at 12:42

score 47 · Accepted Answer · answered Jun 04 '14 at 20:59

47

There's no way to do this using String interpolation.

You can find a good discussion about this on this Apple Dev Forum post.

You can use NSNumberFormatter or NSDateFormatter to format the output.

Alternatively, to use printf-like syntax, you can still use NSString:

var str = NSString(format: "Hello, world %.2f", 42.12312312313)

answered Jun 04 '14 at 20:59

Cezary Wojcik

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FYI, your link appears to have experienced linkrot. – RonLugge Sep 29 '17 at 23:31
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**Swift5** String(format: "%.2f", arguments: [count]) – uplearned.com Oct 29 '19 at 10:08

score 32 · Answer 2 · edited Jan 09 '20 at 08:43

32

Unsure if there is a pure Swift-way but you can always use NSStrings +stringWithFormat::

let str = String(format: "%.2f", 1.23)

edited Jan 09 '20 at 08:43

Valentin Shamardin

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answered Jun 04 '14 at 20:59

hallski

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For something as simple as this example, this is a perfectly good solution. – NRitH Jul 02 '14 at 01:50
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You may use String not NSString : let str = String(format: "%.2f", 1.23) – Sébastien REMY Jul 28 '16 at 07:47

String formatting of a Double

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