@Contract

The @Contract decorator is the foundational decorator that marks a TypeScript class as a smart contract. Every smart contract must have exactly one class decorated with @Contract.

Syntax

@Contract
export class MyContract {
  // Contract implementation
}

Purpose

The @Contract decorator:

• Identifies Contract Classes: Tells the compiler which class represents the smart contract
• Enables Contract Features: Allows the use of other decorators like @External, @View, etc.
• Generates Entry Points: Creates the necessary WASM entry points for Stylus execution
• ABI Generation: Enables automatic ABI (Application Binary Interface) generation

Rules and Constraints

Single Contract Rule

• One per file: Each contract file must contain exactly one @Contract decorated class
• No multiple contracts: Multiple @Contract decorators in the same file will cause compilation errors

// ✅ Valid - Single contract
@Contract
export class MyContract {
  // Implementation
}

// ❌ Invalid - Multiple contracts
@Contract
export class FirstContract { }

@Contract  // Error: Multiple contracts not allowed
export class SecondContract { }

Class Structure

• Export Required: The contract class must be exported
• Static Members: Contract storage and methods should typically be static
• Constructor Support: Optional constructor for initialization logic

Basic Example

@Contract
export class SimpleStorage {
  
  @View
  static getValue(): U256 {
    return U256Factory.fromString("1");
  }
}

Advanced Usage

With Constructor

@Contract
export class Counter {
  static count: U256;

  constructor() {
    count = U256Factory.create();
  }

  @External
  static increment(): void {
    count = count.add(U256Factory.fromString("1"));
  }

  @View
  static getCount(): U256 {
    return count;
  }
}

Compilation Process

When you use @Contract, the compiler:

1. Validates Structure: Ensures only one contract per file
2. Processes Methods: Identifies @External, @View, and other decorated methods
3. Generates Entry Points: Creates WASM entry points for external methods
4. Creates ABI: Generates JSON ABI for external interaction
5. Optimizes Code: Performs AssemblyScript optimizations for Stylus

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🎯 More Decorators

@ContractDefine your smart contract@ExternalPublic contract methods@ViewRead-only methods@EventBlockchain event logging@ErrorCustom error definitionsVisibility and State MutabilityMethod visibility control