String formatting of a Double [duplicate]

问题

This question already has answers here:

Precision String Format Specifier In Swift (30 answers)

Closed 5 years ago.

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!

回答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)

回答2:

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

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

来源：https://stackoverflow.com/questions/24047374/string-formatting-of-a-double