Extracting from Data

FromData type class is used to convert a Data value to a Scalus value.


import scalus.builtin.*, Builtins.*, Data.*
 
case class Account(hash: ByteString, balance: BigInt)
 
enum State:
    case Empty
    case Active(account: Account)
 
 
val fromDataExample = compile {
    // The `fromData` function is used to convert a `Data` value to a Scalus value.
    val data = iData(123)
    // fromData is a summoner method for the `FromData` type class
    // there are instances for all built-in types
    val a = fromData[BigInt](data)
    // also you can use extension method `to` on Data
    val b = data.to[BigInt]
 
    // you can define your own `FromData` instances
    {
        given FromData[Account] = (d: Data) => {
            val args = unConstrData(d).snd
            Account(args.head.to[ByteString], args.tail.head.to[BigInt])
        }
        val account = data.to[Account]
    }
 
    // or your can you a macro to derive the FromData instance
    {
        given FromData[Account] = FromData.derived
        given FromData[State] = FromData.derived
    }
}

You can derive FromData instances for your case classes and enums via standard Scala 3 derives syntax. One caveat - you must always supply companion object with @Compile annotation on it even if it is empty. This is because Scalus needs to compile the companion object to include the FromData instance in the UPLC script.


import scalus.builtin.*, Builtins.*, Data.*
 
case class Account(hash: ByteString, balance: BigInt) derives FromData, ToData
 
@Compile
object Account
 
enum State derives FromData, ToData:
    case Empty
    case Active(account: Account2)
 
@Compile
object State