Direct access to Script Context fields

When working with Cardano validators, you often need to access specific fields from the ScriptContext rather than processing the entire structure. Scalus provides efficient ways to extract only the data you need.

Instead of converting the full ScriptContext to Scott-encoded lambdas (which can be verbose and inefficient), you can use the fieldAsData macro or the .field extension method to directly access specific fields from a Data object representing a complex structure like ScriptContext.


import scalus.*, Compiler.*, builtin.{Data, Builtins, ByteString}, Builtins.*, ByteString.given
import scalus.ledger.api.v3.*
 
val sir = compile:
    def validator(ctxData: Data) =
        // this generates headList(...headList(sndPair(unConstrData(ctxData)))) code
        // to extract the signatories field from the ScriptContext
        val signatories = fieldAsData[ScriptContext](_.txInfo.signatories)(ctxData)
        // or like this, which is equivalent
        val signatories2 = ctxData.field[ScriptContext](_.txInfo.signatories)
        val sigs = unListData(signatories)
        // or like this, which is equivalent
        val sigs2 = signatories2.toList
        unBData(sigs.head) == hex"deadbeef"
        // same as above
        sigs2.head.toByteString == hex"deadbeef"