Passing StringBuilder::append as argument in Kotlin

Question

I'm using BIP39 plugin for Java to create a mnemonic. So I've converted (well mostly IDEA did) this Java code to a function in Kotlin syntax which looks like this:

fun mnemonicBuilder(): String {
  val sb = StringBuilder()
  val entropy = ByteArray(Words.TWELVE.byteLength())
  SecureRandom().nextBytes(entropy)
  MnemonicGenerator(English.INSTANCE)
      .createMnemonic(entropy, sb::append)
  return sb.toString()
}

IntelliJ IDEA keeps telling me that "None of the following functions can be called with the arguments supplied." for sb::append.

My quess is that .createMnemonic requires the second argument to have no return value (given by Target interface) but all appenders return the StringBuilder as a value.

Please, can somebody help me?

There is a concise Kotlin implementation of bip-39 that you might find helpful so that you're not having to rely on IntelliJ to convert Java to Kotlin. I created it to support Android wallet work and it is mainly based off a Rust-implementation from one of our in-house cryptographers who is a co-author on the BIP-39 spec. The library has also passed review by our security team. So hopefully it is useful. If not, file an issue :) — gMale
– gMale, Commented Sep 1, 2020 at 16:58

Mafor · Accepted Answer · 2020-08-11 12:31:52Z

2

Indeed, argument signatures do not match. You can solve it by using lambda instead of the method reference:

MnemonicGenerator(English.INSTANCE)
    .createMnemonic(entropy) { sb.append(it) }

answered Aug 11, 2020 at 12:31

Mafor

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