Fee delegation without using raw transaction

English Caver
1

Hello,

I understand with caver it’s possible to use fee delegation (FD) while building a raw transaction. But for my workflow I’m looking to use the fee delegation directly from the contract method.

const contract = new caver.klay.Contract(MINTABLE, this.manager.arguments.contract, {gasLimit: 1000000})
        contract.methods.mintTo(this.manager.arguments.to).send({ from: sender.address, gas: '3000000',type:'FEE_DELEGATED_SMART_CONTRACT_EXECUTION' }).then()

But this return Error: Unsupported transaction type. Please use SMART_CONTRACT_EXECUTION or SMART_CONTRACT_DEPLOY.

Is there a way to use FD directly on the contract methods ?

2

Hello, thanks for the question first. :slight_smile:

Unfortunately, for now FD type transactions cannot be used directly in the current contract.

If you want to use FD, you need to create a FEE_DELEGATED_SMART_CONTRACT_EXECUTION type transaction and send it to the network.

Please refer to the example code below. In the code below. When creating a transaction, change the value set in data field to match the function of the contract you want to call.

const caver = new Caver('https://api.baobab.klaytn.net:8651/')
const sender = caver.klay.accounts.wallet.add('0x{private key}')
const feePayer = caver.klay.accounts.wallet.add('0x{private key}')

const contactAddress = '0x{contract address}'

const fdTransaction = {
    type: 'FEE_DELEGATED_SMART_CONTRACT_EXECUTION',
    from: sender.address,
    to: contactAddress,
    data: caver.klay.abi.encodeFunctionCall(
        {
            constant: false,
            inputs: [{ name: 'account', type: 'address' }, { name: 'amount', type: 'uint256' }],
            name: 'mint',
            outputs: [{ name: '', type: 'bool' }],
            payable: false,
            stateMutability: 'nonpayable',
            type: 'function',
        },
        ['0x7fbe0f15b48b45475fef618e8f82d61a3f04807d', 10]
    ),
    gas: 100000,
}

// Sign transaction as a sender.
const signed = await caver.klay.accounts.signTransaction(fdTransaction)
console.log(signed)

// Sign transaction as a fee payer with RLP-encoded string that includes signature of sender(signed.rawTransaction)
const feePayerSigned = await caver.klay.accounts.feePayerSignTransaction(signed.rawTransaction, feePayer.address)
console.log(feePayerSigned)

const receipt = await caver.klay.sendSignedTransaction(feePayerSigned)
console.log(receipt)
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