First Smart Contract

Creating a new validator from the template

Let’s seed a new Scalus validator:

sbt new scalus3/validator.g8

This ran the template scalus/validator.g8 using Giter8 . When prompted, name the application htlc validator. This command scaffolds a simple Scalus validator project.

sbt new scalus3/validator.g8
 
name [MyValidator]: htlc validator
 
Template applied in ./htlc-validator

Project structure

Let’s take a look at what just got generated:

 htlc-validator/
    ├── HtlcValidator.scala        # Simple validator
    ├── HtlcValidator.test.scala   # Simple tests
    ├── project.scala              # Project configuration
    └── README.md

HTLC Contract

Let’s create a simple “Hello Cardano” validator script that verifies a specific message:

Create or open the file src/main/scala/com/example/contracts/HelloCardano.scala:

...

This simple validator script demonstrates several key concepts:

• The @OnChain annotation marks the class for on-chain compilation
• The validate method defines the validation logic
• Contract params, Datum, Redeemer
• We’re using the ScriptContext to access transaction information

Let’s test our Smart Contract

Debugging Smart Contract

Breakpoint

Building Plutus script

sbt compile

Build? Blueprint

Evaluating Script

Now let’s create a simple client to interact with our smart contract:

Create or open the file src/main/scala/com/example/offchain/Client.scala

...