Version: SDK V2

Mint your NFT on Multiple chains with one signature

In this guide, we will edit the functionality in the gasless transaction section to switch from minting an NFT on one chain to two chains with one signature.

We will mint the NFT on both Polygon and Base testnetworks. If you are using the bundler and Paymaster URLs in this tutorial you will not need to do anything on the Dashboard. If you are following along with your own contract make sure to register your new contracts on Base as well as Polygon. In our case our contract is the same address on both networks (0x1758f42Af7026fBbB559Dc60EcE0De3ef81f665e).

Click to view code from previous section

import { config } from "dotenv";
import { IBundler, Bundler } from "@biconomy/bundler";
import { ChainId } from "@biconomy/core-types";
import {
  BiconomySmartAccountV2,
  DEFAULT_ENTRYPOINT_ADDRESS,
} from "@biconomy/account";
import {
  ECDSAOwnershipValidationModule,
  DEFAULT_ECDSA_OWNERSHIP_MODULE,
} from "@biconomy/modules";
import { ethers } from "ethers";
import {
  IPaymaster,
  BiconomyPaymaster,
  IHybridPaymaster,
  PaymasterMode,
  SponsorUserOperationDto,
} from "@biconomy/paymaster";

config();

const provider = new ethers.providers.JsonRpcProvider(
  "https://rpc.ankr.com/polygon_mumbai"
);
const wallet = new ethers.Wallet(process.env.PRIVATE_KEY || "", provider);

const bundler: IBundler = new Bundler({
  bundlerUrl: "https://bundler.biconomy.io/api/v2/80001/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44",
  chainId: ChainId.POLYGON_MUMBAI,
  entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
});

const paymaster: IPaymaster = new BiconomyPaymaster({
  paymasterUrl: "https://paymaster.biconomy.io/api/v1/80001/Tpk8nuCUd.70bd3a7f-a368-4e5a-af14-80c7f1fcda1a",
});

async function createAccount() {
  const module = await ECDSAOwnershipValidationModule.create({
    signer: wallet,
    moduleAddress: DEFAULT_ECDSA_OWNERSHIP_MODULE,
  });

  let biconomyAccount = await BiconomySmartAccountV2.create({
    chainId: ChainId.POLYGON_MUMBAI,
    bundler: bundler,
    paymaster: paymaster,
    entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
    defaultValidationModule: module,
    activeValidationModule: module,
  });
  console.log("address", await biconomyAccount.getAccountAddress());
  return biconomyAccount;
}

async function mintNFT() {
  const smartAccount = await createAccount();
  const address = await smartAccount.getAccountAddress();
  const nftInterface = new ethers.utils.Interface([
    "function safeMint(address _to)",
  ]);

  const data = nftInterface.encodeFunctionData("safeMint", [address]);

  const nftAddress = "0x1758f42Af7026fBbB559Dc60EcE0De3ef81f665e";

  const transaction = {
    to: nftAddress,
    data: data,
  };

  let partialUserOp = await smartAccount.buildUserOp([transaction], {
    paymasterServiceData: {
      mode: PaymasterMode.SPONSORED,
    },
  });

  const biconomyPaymaster =
    smartAccount.paymaster as IHybridPaymaster<SponsorUserOperationDto>;

  try {
    const paymasterAndDataResponse =
      await biconomyPaymaster.getPaymasterAndData(partialUserOp);
    partialUserOp.paymasterAndData = paymasterAndDataResponse.paymasterAndData;
  } catch (e) {
    console.log("error received ", e);
  }

  try {
    const userOpResponse = await smartAccount.sendUserOp(partialUserOp);
    const transactionDetails = await userOpResponse.wait();
    console.log(
      `transactionDetails: https://mumbai.polygonscan.com/tx/${transactionDetails.receipt.transactionHash}`
    );
    console.log(
      `view minted nfts for smart account: https://testnets.opensea.io/${address}`
    );
  } catch (e) {
    console.log("error received ", e);
  }
}

mintNFT();

Switch to MultiChain Validator

Let's update the import for the modules and switch over to the Multichain Validator:

import { MultiChainValidationModule, DEFAULT_MULTICHAIN_MODULE } from "@biconomy/modules";

Now lets change the module:

const multiChainModule = await MultiChainValidationModule.create({
    signer: signer,
    moduleAddress: DEFAULT_MULTICHAIN_MODULE
  })

Remember to update your Smart Account Config as well:

const biconomySmartAccountConfig1 = {
    signer: signer,
    chainId: ChainId.POLYGON_MUMBAI,
    paymaster: paymaster, 
    bundler: bundler, 
    entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
    defaultValidationModule: multiChainModule,
    activeValidationModule: multiChainModule
  };

Set up Base

So far we only made changes on the MultiChain Module to work with Polygon. Now lets add support for Base with additional Paymaster, Bundler, and Smart Account Instance:

   const baseBundler = new Bundler({
    bundlerUrl: "https://bundler.biconomy.io/api/v2/84531/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44",
    chainId: config.chainId,
    entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
  });

  const basePaymaster: IPaymaster = new BiconomyPaymaster({
  paymasterUrl: 'https://paymaster.biconomy.io/api/v1/84531/m814QNmpW.fce62d8f-41a1-42d8-9f0d-2c65c10abe9a' 
})

Let's create a new connect function and name it createBaseAccount. It should look something like this:

async function createBaseAccount() {
  
}

Now add the following in your base function in order to initialize an instance of your Smart Account on Base, you should also copy over the module creation as well. Lets return both the module and account here.

  const multiChainModule = await MultiChainValidationModule.create({
    signer: wallet,
    moduleAddress: DEFAULT_MULTICHAIN_MODULE,
  });

  let baseAccount = await BiconomySmartAccountV2.create({
    chainId: ChainId.BASE_GOERLI_TESTNET,
    paymaster: basePaymaster, 
    bundler: baseBundler, 
    entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
    defaultValidationModule: multiChainModule,
    activeValidationModule: multiChainModule
  });

  return { baseAccount, multiChainModule}

Now in the mint NFT function after updating the paymaster data for the polygon userOp lets do the same for base:

  const { baseAccount, multiChainModule } = await createBaseAccount()

  const baseAddress = await baseAccount.getAccountAddress();

  const data2 = nftInterface.encodeFunctionData("safeMint", [baseAddress]);

  const transaction2 = {
    to: nftAddress,
    data: data2,
  };

  let partialUserOp2 = await baseAccount.buildUserOp([transaction2], {
    paymasterServiceData: {
      mode: PaymasterMode.SPONSORED,
    }
  });

  const basePaymaster = baseAccount.paymaster as IHybridPaymaster<SponsorUserOperationDto>;

  try {
    const paymasterAndDataResponse =
      await basePaymaster.getPaymasterAndData(partialUserOp2);
      partialUserOp2.paymasterAndData = paymasterAndDataResponse.paymasterAndData;
  } catch (e) {
    console.log("error received ", e);
  }

const returnedOps = await multiChainModule.signUserOps([{userOp: partialUserOp, chainId: ChainId.POLYGON_MUMBAI}, {userOp: partialUserOp2, chainId: ChainId.BASE_GOERLI_TESTNET}]);

Finally lets update the the try catch block to execute our mint on both networks:

  try {
    const userOpResponse1 = await smartAccount.sendSignedUserOp(returnedOps[0]);
    const transactionDetails = await userOpResponse1.wait();
    console.log(
      `transactionDetails: https://mumbai.polygonscan.com/tx/${transactionDetails.receipt.transactionHash}`
    );
    console.log(
      `view minted nfts for smart account: https://testnets.opensea.io/${address}`
    );
  } catch (e) {
    console.log("error received ", e);
  }

  try {
    const userOpResponse2 = await baseAccount.sendSignedUserOp(returnedOps[1]);
    const transactionDetails = await userOpResponse2.wait();
    console.log(
      `transactionDetails: https://goerli.basescan.org/tx/${transactionDetails.receipt.transactionHash}`
    );
    console.log(
      `view minted nfts for smart account: https://testnets.opensea.io/${address}`
    );
  } catch (e) {
    console.log("error received ", e);
  }

We're excited to see what you build with the multi chain validation module!

Click to view the final code for this section

import { config } from "dotenv";
import { IBundler, Bundler } from "@biconomy/bundler";
import { ChainId } from "@biconomy/core-types";
import {
  BiconomySmartAccountV2,
  DEFAULT_ENTRYPOINT_ADDRESS,
} from "@biconomy/account";
import {
  MultiChainValidationModule,
  DEFAULT_MULTICHAIN_MODULE,
} from "@biconomy/modules";
import { ethers } from "ethers";
import {
  IPaymaster,
  BiconomyPaymaster,
  IHybridPaymaster,
  PaymasterMode,
  SponsorUserOperationDto,
} from "@biconomy/paymaster";

config();

const provider = new ethers.providers.JsonRpcProvider(
  "https://rpc.ankr.com/polygon_mumbai"
);
const wallet = new ethers.Wallet(process.env.PRIVATE_KEY || "", provider);

const bundler: IBundler = new Bundler({
  bundlerUrl:
    "https://bundler.biconomy.io/api/v2/80001/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44",
  chainId: ChainId.POLYGON_MUMBAI,
  entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
});

const paymaster: IPaymaster = new BiconomyPaymaster({
  paymasterUrl:
    "https://paymaster.biconomy.io/api/v1/80001/Tpk8nuCUd.70bd3a7f-a368-4e5a-af14-80c7f1fcda1a",
});

const baseBundler = new Bundler({
  bundlerUrl: "https://bundler.biconomy.io/api/v2/84531/nJPK7B3ru.dd7f7861-190d-41bd-af80-6877f74b8f44",
  chainId: ChainId.BASE_GOERLI_TESTNET,
  entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
});

const basePaymaster: IPaymaster = new BiconomyPaymaster({
paymasterUrl: 'https://paymaster.biconomy.io/api/v1/84531/m814QNmpW.fce62d8f-41a1-42d8-9f0d-2c65c10abe9a' 
})


async function createAccount() {
  const multiChainModule = await MultiChainValidationModule.create({
    signer: wallet,
    moduleAddress: DEFAULT_MULTICHAIN_MODULE,
  });

  const biconomySmartAccountConfig1 = {
    signer: wallet,
    chainId: ChainId.POLYGON_MUMBAI,
    paymaster: paymaster,
    bundler: bundler,
    entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
    defaultValidationModule: multiChainModule,
    activeValidationModule: multiChainModule,
  };

  let biconomyAccount = await BiconomySmartAccountV2.create(biconomySmartAccountConfig1);
  console.log("address", await biconomyAccount.getAccountAddress());
  return biconomyAccount;
}

async function createBaseAccount() {
  const multiChainModule = await MultiChainValidationModule.create({
    signer: wallet,
    moduleAddress: DEFAULT_MULTICHAIN_MODULE,
  });

  let baseAccount = await BiconomySmartAccountV2.create({
    chainId: ChainId.BASE_GOERLI_TESTNET,
    paymaster: basePaymaster, 
    bundler: baseBundler, 
    entryPointAddress: DEFAULT_ENTRYPOINT_ADDRESS,
    defaultValidationModule: multiChainModule,
    activeValidationModule: multiChainModule
  });

  return { baseAccount, multiChainModule }

}

async function mintNFT() {
  const smartAccount = await createAccount();
  const address = await smartAccount.getAccountAddress();
  const nftInterface = new ethers.utils.Interface([
    "function safeMint(address _to)",
  ]);

  const data = nftInterface.encodeFunctionData("safeMint", [address]);

  const nftAddress = "0x1758f42Af7026fBbB559Dc60EcE0De3ef81f665e";

  const transaction = {
    to: nftAddress,
    data: data,
  };

  let partialUserOp = await smartAccount.buildUserOp([transaction], {
    paymasterServiceData: {
      mode: PaymasterMode.SPONSORED,
    },
  });

  const biconomyPaymaster =
    smartAccount.paymaster as IHybridPaymaster<SponsorUserOperationDto>;
  try {
    const paymasterAndDataResponse =
      await biconomyPaymaster.getPaymasterAndData(partialUserOp);
    partialUserOp.paymasterAndData = paymasterAndDataResponse.paymasterAndData;
  } catch (e) {
    console.log("error received ", e);
  }

  const { baseAccount, multiChainModule } = await createBaseAccount()

  const baseAddress = await baseAccount.getAccountAddress();

  const data2 = nftInterface.encodeFunctionData("safeMint", [baseAddress]);

  const transaction2 = {
    to: nftAddress,
    data: data2,
  };

  let partialUserOp2 = await baseAccount.buildUserOp([transaction2], {
    paymasterServiceData: {
      mode: PaymasterMode.SPONSORED,
    }
  });

  const basePaymaster = baseAccount.paymaster as IHybridPaymaster<SponsorUserOperationDto>;

  try {
    const paymasterAndDataResponse =
      await basePaymaster.getPaymasterAndData(partialUserOp2);
      partialUserOp2.paymasterAndData = paymasterAndDataResponse.paymasterAndData;
  } catch (e) {
    console.log("error received ", e);
  }

  const returnedOps = await multiChainModule.signUserOps([{userOp: partialUserOp, chainId: ChainId.POLYGON_MUMBAI}, {userOp: partialUserOp2, chainId: ChainId.BASE_GOERLI_TESTNET}]);

  try {
    const userOpResponse1 = await smartAccount.sendSignedUserOp(returnedOps[0]);
    const transactionDetails = await userOpResponse1.wait();
    console.log(
      `transactionDetails: https://mumbai.polygonscan.com/tx/${transactionDetails.receipt.transactionHash}`
    );
    console.log(
      `view minted nfts for smart account: https://testnets.opensea.io/${address}`
    );
  } catch (e) {
    console.log("error received ", e);
  }

  try {
    const userOpResponse2 = await baseAccount.sendSignedUserOp(returnedOps[1]);
    const transactionDetails = await userOpResponse2.wait();
    console.log(
      `transactionDetails: https://goerli.basescan.org/tx/${transactionDetails.receipt.transactionHash}`
    );
    console.log(
      `view minted nfts for smart account: https://testnets.opensea.io/${address}`
    );
  } catch (e) {
    console.log("error received ", e);
  }


}

mintNFT();

Mint your NFT on Multiple chains with one signature

Switch to MultiChain Validator​

Set up Base​

Switch to MultiChain Validator

Set up Base