Creating UserOperations

This part walks over how to use the SDK to produce various kinds of UserOperations.

Understanding Minimal UserOperations

User operations have a standard structure, hence it’s crucial to know before starting certain transactions. A simple user operation includes all necessary fields even with placeholder values:

// Create a minimal UserOp
const minimalUserOp = {
  sender: aaWalletAddress, // The AA wallet address
  nonce: "0x0",            // Will be filled by the SDK or custom logic
  initCode: "0x",          // Empty for existing wallets
  callData: "0x",          // Will be filled with actual transaction data
  callGasLimit: "0x0",     // Gas estimation
  verificationGasLimit: "0x0",
  preVerificationGas: "0x0",
  maxFeePerGas: "0x0",
  maxPriorityFeePerGas: "0x0",
  paymasterAndData: "0x",  // Will be filled by Paymaster integration
  signature: "0x"          // Will be filled with EOA signature
};

This minimal structure is useful for:

Making RPC calls that require a UserOperation structure
Initializing a UserOperation before filling in specific details
Testing and debugging
Interacting with services like the Paymaster API

The UserOpSDK will handle filling in most of these fields automatically, but understanding this structure is helpful when working with the SDK and developing your own utilities.

Simple Token Transfer

To perform a simple ERC-20 token transfer, you’ll start with the builder created in the Basic Usage section and add your specific transaction:

// 1. Start with the builder from previous setup
// const builder = await Presets.Builder.SimpleAccount.init(...);
 
// 2. Create an ERC-20 contract instance
const tokenContract = new ethers.Contract(
  tokenAddress,
  ['function transfer(address to, uint256 amount) returns (bool)'],
  accountSigner
);
 
// 3. Prepare the call data for transfer
const callData = tokenContract.interface.encodeFunctionData(
  'transfer',
  [recipientAddress, ethers.utils.parseUnits(amount, decimals)]
);
 
// 4. Add the transaction to the builder
// This will incorporate the transaction into a UserOperation
builder.execute(tokenAddress, 0, callData);
 
// 5. The builder now contains the UserOperation with your transfer
// Under the hood, it fills in the parameters of the minimal UserOperation:
// - sender: from builder.getSender()
// - nonce: auto-retrieved from the AA wallet
// - callData: your transfer function call
// - gas parameters: estimated or set manually

When you call builder.execute(), the SDK takes care of incorporating your transaction into the UserOperation structure, eliminating the need to manually build each field of the minimal UserOperation.

Executing Multiple Transactions

You can bundle multiple actions into a single UserOperation using the same builder pattern:

// 1. Start with the same builder
// const builder = await Presets.Builder.SimpleAccount.init(...);
 
// 2. Prepare multiple call data and targets
const callData = [
  tokenContract.interface.encodeFunctionData('approve', [spender, amount]),
  tokenContract.interface.encodeFunctionData('transfer', [recipient, amount])
];
const callTo = [tokenAddress, tokenAddress];
 
// 3. Add batch execution to the builder
// This bundles multiple transactions into a single UserOperation
builder.executeBatch(callTo, callData);
 
// 4. The builder now contains a UserOperation with multiple actions
// The single UserOperation will:
// - Approve tokens to be spent by another address
// - Transfer tokens to the recipient
// All in one atomic transaction

With the batch execution feature, multiple actions are combined into a single UserOperation’s callData field, allowing you to perform complex operations efficiently.

Next Steps

After creating UserOperations with the builder:

Integrate with Paymaster to handle gas payments
Send UserOperations to the network

Working with AA Wallets Paymaster Integration