Format in kotlin string templates

Unfortunately, there's no built-in support for formatting in string templates yet, as a workaround, you can use something like:

"pi = ${pi.format(2)}"

the .format(n) function you'd need to define yourself as

fun Double.format(digits: Int) = "%.${digits}f".format(this)

This will work only in Kotlin/JVM.

There's clearly a piece of functionality here that is missing from Kotlin at the moment, we'll fix it.

It's simple, use:

val str: String = "%.2f".format(3.14159)

As a workaround, There is a Kotlin stdlib function that can be used in a nice way and fully compatible with Java's String format (it's only a wrapper around Java's String.format())

See Kotlin's documentation

Your code would be:

val pi = 3.14159265358979323
val s = "pi = %.2f".format(pi)

Kotlin's String class has a format function now, which internally uses Java's String.format method:

/**
 * Uses this string as a format string and returns a string obtained by substituting the specified arguments,
 * using the default locale.
 */
@kotlin.internal.InlineOnly
public inline fun String.Companion.format(format: String, vararg args: Any?): String = java.lang.String.format(format, *args)

Usage

val pi = 3.14159265358979323
val formatted = String.format("%.2f", pi) ;
println(formatted)
>>3.14