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!

Solution 1

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)

Solution 2

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

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

Comments

[Rob]

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).

[NRitH]

For something as simple as this example, this is a perfectly good solution.

[Sébastien REMY]

You may use String not NSString : let str = String(format: "%.2f", 1.23)

[RonLugge]

FYI, your link appears to have experienced linkrot.

[uplearned.com]

Swift5 String(format: "%.2f", arguments: [count])