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Contract Writes with EIP-7702

The guide below demonstrates how to perform Contract Writes with EIP-7702 to invoke Contract functions on an Externally Owned Account.

Overview

Here is an end-to-end overview of how to perform a Contract Write to send a batch of Calls. We will break it down into Steps below.

example.ts
import { getContract, parseEther } from 'viem'
import { walletClient } from './config'
import { abi, contractAddress } from './contract'
 
// 1. Set up a Contract Instance pointing to our Account.
const batchCallInvoker = getContract({
  abi,
  address: walletClient.account.address,
  client: walletClient,
})
 
// 2. Authorize injection of the Contract's bytecode into our Account.
const authorization = await walletClient.signAuthorization({
  contractAddress,
})
 
// 3. Invoke the Contract's `execute` function to perform batch calls.
const hash = await batchCallInvoker.write.execute([{
  data: '0x',
  to: '0xcb98643b8786950F0461f3B0edf99D88F274574D', 
  value: parseEther('0.001'), 
}, {
  data: '0x',
  to: '0xd2135CfB216b74109775236E36d4b433F1DF507B', 
  value: parseEther('0.002'), 
}], {
  authorizationList: [authorization],
  //                  ↑ 4. Pass the Authorization as an option.
})

Steps

0. Install & Run Anvil

EIP-7702 is currently not supported on Ethereum Mainnet or Testnets, so let's set up an EIP-7702 compatible network. We will use an Anvil node for this example. If you are using an existing EIP-7702 compatible network, you can skip this step.

curl -L https://foundry.paradigm.xyz | bash
anvil --hardfork prague

1. Set up Smart Contract

We will need to set up a Smart Contract to interact with. For the purposes of this guide, we will create and deploy a BatchCallInvoker.sol contract, however, you can use any existing deployed contract.

Firstly, deploy a Contract to the Network with the following source:

BatchCallInvoker.sol
pragma solidity ^0.8.20;
 
contract BatchCallInvoker {
  struct Call {
    bytes data;
    address to;
    uint256 value;
  }
 
  function execute(Call[] calldata calls) external payable {
    for (uint256 i = 0; i < calls.length; i++) {
      Call memory call = calls[i];
      (bool success, ) = call.to.call{value: call.value}(call.data);
      require(success, "call reverted");
    }
  }
}

2. Set up Client & Account

Next, we will need to set up a Client and Externally Owned Account to sign EIP-7702 Authorizations.

This code snippet uses the Extending Client guide.

config.ts
import { createWalletClient, http } from 'viem'
import { anvil } from 'viem/chains'
import { privateKeyToAccount } from 'viem/accounts'
import { eip7702Actions } from 'viem/experimental'
 
export const account = privateKeyToAccount('0x...')
 
export const walletClient = createWalletClient({
  account,
  chain: anvil,
  transport: http(),
}).extend(eip7702Actions())

3. Instantiate a Contract Instance

We will instantiate a Contract Instance for our BatchCallInvoker contract.

example.ts
import { getContract } from 'viem'
import { walletClient } from './config'
import { abi } from './contract'
 
const batchCallInvoker = getContract({ 
  abi, 
  address: walletClient.account.address, 
  walletClient, 
})

4. Authorize Contract Bytecode Injection

We will need to sign an Authorization to authorize the injection of the Contract's bytecode onto the Account.

In the example below, we are using the account attached to the walletClient to sign the Authorization – this will be the Account that the Contract's bytecode will be injected into.

example.ts
import { getContract } from 'viem'
import { walletClient } from './config'
import { abi, contractAddress } from './contract'
 
const batchCallInvoker = getContract({
  abi,
  address: walletClient.account.address,
  walletClient,
})
 
const authorization = await walletClient.signAuthorization({ 
  contractAddress, 
})

5. Invoke Contract Function

Using our Contract Instance, we can now call the execute function on it to perform batch calls.

example.ts
import { getContract, parseEther } from 'viem'
import { walletClient } from './config'
import { abi, contractAddress } from './contract'
 
const batchCallInvoker = getContract({
  abi,
  address: walletClient.account.address,
  walletClient,
})
 
const authorization = await walletClient.signAuthorization({
  contractAddress,
})
 
const hash = await batchCallInvoker.write.execute([{ 
  data: '0x', 
  to: '0xcb98643b8786950F0461f3B0edf99D88F274574D', 
  value: parseEther('0.001'), 
}, { 
  data: '0x', 
  to: '0xd2135CfB216b74109775236E36d4b433F1DF507B', 
  value: parseEther('0.002'), 
}], { 
  authorizationList: [authorization], 
})

6. Optional: Use an Invoker

We can also utilize an Invoker Account to execute a call on behalf of the authorizing Account. This is useful for cases where we want to "sponsor" the Transaction for the user (i.e. pay for their gas fees).

example.ts
import { getContract, parseEther } from 'viem'
import { walletClient } from './config'
import { abi, contractAddress } from './contract'
 
const batchCallInvoker = getContract({
  abi,
  address: walletClient.account.address,
  walletClient,
})
 
const authorization = await walletClient.signAuthorization({
  contractAddress,
})
 
const invoker = privateKeyToAccount('0x...') 
 
const hash = await batchCallInvoker.write.execute([{
  data: '0x',
  to: '0xcb98643b8786950F0461f3B0edf99D88F274574D',
  value: parseEther('0.001'),
}, {
  data: '0x',
  to: '0xd2135CfB216b74109775236E36d4b433F1DF507B',
  value: parseEther('0.002'),
}], {
  account: invoker, 
  authorizationList: [authorization],
})