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SmartContract Basics

The SmartContract class is the foundation for building zkApps. It provides the framework for defining state, methods, and behavior of your zero-knowledge smart contracts.

Basic Structure​

Every zkApp extends the SmartContract class and follows this basic pattern:

export class SimpleCounter extends SmartContract {
  @state(Field) counter = State<Field>();

  @method async increment() {
    const currentCounter = this.counter.getAndRequireEquals();
    this.counter.set(currentCounter.add(1));
  }
}

Key components include state variables declared with @state(Type), an init() method for setup, and public methods marked with @method.

State Management​

zkApps can have multiple state variables of different types:

export class MultiStateContract extends SmartContract {
  @state(Field) counter = State<Field>();
  @state(Bool) isActive = State<Bool>();
  @state(UInt32) lastUpdate = State<UInt32>();

  @method async updateState(newCounter: Field) {
    // Check that contract is active
    const active = this.isActive.getAndRequireEquals();
    active.assertTrue();

    // Update counter
    this.counter.set(newCounter);
    
    // Update timestamp
    this.lastUpdate.set(UInt32.from(Date.now()));
  }
}

State operations include get(), getAndRequireEquals(), set(), and requireEquals().

API Reference​

For detailed information about the SmartContract class, see: