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How to integrate Fee Delegation features into wallets

Thanks to Kaia’s native fee delegation feature, users can enjoy gas-less transactions on dApps. However, to enable this functionality, wallets must support fee-delegated transaction types. This guide explains how wallet providers can integrate fee delegation capabilities into their wallets.

To integrate fee delegation, wallet providers should:

1. Add the Kaia SDK (for example, kaiachain/ethers-ext) to your codebase.
2. Whenever the RPC method of the wallet provider, kaia_signTransaction, is called, use the Kaia SDK to sign the transaction.
3. As a result, the wallet should return the signed transaction, senderTxHashRlp, to the dApp instead of sending it directly to the node provider. It will be transferred to the fee payer.

Below is a basic example for a simple value transfer:

const ethers = require("ethers6");

const { Wallet, TxType, parseKaia } = require("@kaiachain/ethers-ext/v6");

const senderAddr = "0xa2a8854b1802d8cd5de631e690817c253d6a9153";

const senderPriv = "0x0e4ca6d38096ad99324de0dde108587e5d7c600165ae4cd6c2462c597458c2b8";

const recieverAddr = "0xc40b6909eb7085590e1c26cb3becc25368e249e9";

const provider = new ethers.JsonRpcProvider( "https://public-en-kairos.node.kaia.io" );

const senderWallet = new Wallet(senderPriv, provider);

async function main() {

const tx = {

type: TxType.FeeDelegatedValueTransfer,

from: senderAddr,

to: recieverAddr,

value: parseKaia("0.01"),

};

// Sign transaction by sender

const populatedTx = await senderWallet.populateTransaction(tx);

const senderTxHashRLP = await senderWallet.signTransaction(populatedTx); console.log("senderTxHashRLP", senderTxHashRLP);

}

For contract interactions:

const ethers = require("ethers6");

const { Wallet, TxType, parseKaia } = require("@kaiachain/ethers-ext/v6");

const senderAddr = "0xa2a8854b1802d8cd5de631e690817c253d6a9153";

const senderPriv = "0x0e4ca6d38096ad99324de0dde108587e5d7c600165ae4cd6c2462c597458c2b8";

const provider = new ethers.JsonRpcProvider( "https://public-en-kairos.node.kaia.io" );

const senderWallet = new Wallet(senderPriv, provider);

const contractAddr = "0x95Be48607498109030592C08aDC9577c7C2dD505";

const abi = ["function setNumber(uint256 newNumber)"];

async function main() {

const contract = new ethers.Contract(contractAddr, abi, provider);

const data = contract.interface.encodeFunctionData("setNumber", ["0x123"]);

const tx = {

type: TxType.FeeDelegatedSmartContractExecution,

from: senderAddr,

to: recieverAddr,

value: 0,

data: data,

};

// Sign transaction by sender

const populatedTx = await senderWallet.populateTransaction(tx);

const senderTxHashRLP = await senderWallet.signTransaction(populatedTx); console.log("senderTxHashRLP", senderTxHashRLP);

}

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The exact integration code may vary depending on your wallet’s implementation.