How to charge a fee on each transaction

FunWallet let you execute transactions on any EVM chain and provides a straightforward method of charging a fee on each transaction to monetize FunWallets. In this guide, I will show you how to create a fee that is charged to your FunWallet.

We have to import configureEnvironment to set up the environment.

import { configureEnvironment } from "@funkit/core";

The FunWallet environment is where we configure the developer fee. I’ll first explain the basic environment variables that we need to input:

configureEnvironment({
  chain: "goerli",
  apiKey: "ZrhepzWGxm74D0sqstuhT6dGrJxhoy8SZIToX6I3",
});

There are a couple of options FunWallet have for creating a developer fee. In the FunWallet environment, we can set up either a fixed fee or a percentage fee. Let me describe how to set it up.

Let’s charge with a fixed fee of 0.001 ETH on each transaction. These are the parameters we will need to set up.

configureEnvironment({
  fee: {
    token: "eth",
    amount: 0.001,
    recipient: "0x2167F5F1F3570F17112E938d8C2237b2e412e075",
  },
});

We also can use a percentage fee that takes current gas costs in mind. For example, we could set a 5% gas fee like this:

configureEnvironment({
  fee: {
    token: "eth",
    gasPercent: 5,
    recipient: "0x2167F5F1F3570F17112E938d8C2237b2e412e075",
  },
});

Charging a fixed fee and percentage fee are both determined in the FunWallet environment. However, we can also create transaction specific fees that can be customized with specific transaction parameters on a per transaction basis. See the summary for a full flow.

// Charge a 1% fee on each transaction based on volume
const transactionFee = transactionAmount * 0.01;

const txOptions = {
  fee: {
    token: "usdc",
    amount: transactionFee,
    recipient: DEVELOPER_ADDR,
  },
};

Putting together all the pieces we can create a FunWallet environment that charges developers fees.

import { configureEnvironment } from '@funkit/core'

configureEnvironment({
chain: "goerli",
apiKey: "ZrhepzWGxm74D0sqstuhT6dGrJxhoy8SZIToX6I3",
fee: {
token: "eth",
gasPercent: 5,
recipient: "0x2167F5F1F3570F17112E938d8C2237b2e412e075"
}
})

Here's is a full flow of creating a transaction volume fee. I'll also recommend you check out the swap tokens guide for details on how to create the transaction.

import { 
  FunWallet, 
  configureEnvironment, 
  Auth, 
  generatePrivateKey 
} from '@funkit/core'

const API_KEY = "ZrhepzWGxm74D0sqstuhT6dGrJxhoy8SZIToX6I3"
const PRIVATE_KEY = generatePrivateKey()
const DEVELOPER_ADDR = // ENTER YOUR ADDRESS HERE
const options = {
chain: "base-mainnet",
apiKey: API_KEY
}
const swapMatic = async () => {
await configureEnvironment(options)
const auth = new Auth({ privateKey: PRIVATE_KEY })
const userId = await auth.getAddress()
const funWallet = new FunWallet({
users: [{ userId: userId }],
uniqueId: await auth.getWalletUniqueId()
})
const assets = await funWallet.getAssets()
const transactionAmount = 10.00
const transactionFee = transactionAmount * 0.01
const txOptions = {
fee: {
token: "usdc",
amount: transactionFee,
recipient: DEVELOPER_ADDR
}
}
const swapParams = {
tokenIn: "usdc",
inAmount: transactionAmount,
tokenOut: "eth",
}

const swapOp = await funWallet.swap(auth, userId, swapParams, txOptions)
const receipt = await funWallet.executeOperation(auth, swapOp)

console.log(receipt)
}

// Call the swapMatic function to initiate the swap
swapMatic()