Scalus Hello Cardano Smart Contract

A minimal Scalus smart contract, generated from the hello.g8 template.

HelloCardano.scala is a Plutus V3 spending validator that approves spending a UTxO only when the transaction is both signed by the owner stored in the datum and carries the redeemer string "Hello, Cardano!".

Prerequisites

• A JDK (17+)
• Scala CLI and/or sbt

Build & test

The project works with both Scala CLI and sbt.

With Scala CLI:

scala-cli test .
scala-cli compile .
scala-cli fmt .

With sbt:

sbt test
sbt compile

Both tools share the same flat source layout: sources live at the project root and test sources use the .test.scala suffix.

Test backends

HelloCardanoIntegration.test.scala runs against a backend selected by the SCALUS_TEST_ENV environment variable:

sbt test                       # in-memory emulator (default, fast)
SCALUS_TEST_ENV=yaci sbt test  # a local Yaci DevKit node (requires a running Docker daemon)

The same works with Scala CLI, e.g. SCALUS_TEST_ENV=yaci scala-cli test ..

Blueprint & deploy

The sbt build enables the scalus-sbt-plugin, which adds tasks backed by the Contract in HelloCardanoContract.scala:

# Generate a CIP-57 blueprint at
# target/scala-3.3.7/classes/META-INF/scalus/blueprints/HelloCardanoContract.json
sbt blueprint

# Deploy the validator as a reference-script UTxO (needs a Blockfrost key and a funded wallet)
export BLOCKFROST_API_KEY=...        # or pass --blockfrost-key
export CARDANO_MNEMONIC="word1 ..."  # or pass --mnemonic
sbt "deploy HelloCardanoContract --network preview"

Profiling

Set SCALUS_PROFILE=1 to run the tests with on-chain execution profiling enabled. It writes an interactive HTML profile (CPU/memory per source line) to target/profile.html:

SCALUS_PROFILE=1 sbt test

The same works with Scala CLI, e.g. SCALUS_PROFILE=1 scala-cli test ..

Learn more

• Scalus documentation: https://scalus.org
• Examples: https://github.com/nau/scalus/tree/master/scalus-examples