Constructors

This note covers Compact constructors - the initialization logic that runs once when a contract is deployed.

Docs: Writing a Contract

Intuition First

A constructor runs exactly once: when you deploy the contract. Set up your initial state here.

Basic Constructor

pragma language_version 0.22;

import CompactStandardLibrary;

export ledger owner: Bytes<32>;
export ledger count: Uint<64>;

constructor() {
  owner = disclose(callerAddress());
  count = 0;
}

With Parameters

constructor(name: Bytes<32>, maxSupply: Uint<64>) {
  name = disclose(name);
  maxSupply = disclose(maxSupply);
  creator = disclose(callerAddress());
}

What Can Go in a Constructor

• Setting initial values
• Creating empty collections
• Recording deployer

What Cannot Go in a Constructor

• Circuit calls
• Witness calls
• Time-dependent logic

Quick Recap

• Constructor runs once at deployment
• Set initial state, record deployer
• Parameters come from deployment transaction
• Cannot call circuits or witnesses

Cross-Links

• Previous: Explicit Disclosure
• Next: Ledger ADTs
• See also: Writing A Contract