Sponsored Transactions (Fee Payer)

The Kotlin SDK provides support for sponsored transactions also known as fee payer transactions.

The standard flow for sending a sponsored transaction is as follows:

1. Determine upon operation by creating a Transaction
2. The sender signs the transaction
3. The fee payer signs the transaction
4. Submit the transaction

Determine Upon Operation

As seen in previous sections, you can build a transaction using buildSimpleTransaction with the lean transaction builder. For sponsored transactions, specify withFeePayer = true.

val txn =
  aptos.buildSimpleTransaction(
    sender = alice.accountAddress,
    withFeePayer = true,
  ) {
    function = "0x1::coin::transfer"
    typeArgs("0x1::aptos_coin::AptosCoin")
    args(bob.accountAddress, 1_000_000UL)
  }

Sign the Transaction

Once built, the sender signs the transaction using sign.

val aliceAuthenticator =
  aptos.sign(signer = alice, transaction = txn)

Sign the Transaction as Fee Payer

The fee payer signs using signAsFeePayer.

val feePayerAuthenticator =
  aptos.signAsFeePayer(feePayer = sponsor, transaction = txn)

Submit the Transaction

Submit the transaction with both authenticators.

val pendingTxn =
  aptos
    .submitTransaction.simple(
      transaction = txn,
      senderAuthenticator = aliceAuthenticator,
      feePayerAuthenticator = feePayerAuthenticator,
    )
    .expect("Failed to submit transaction")

注意

You can combine fee payer signing and submission using signAndSubmitAsFeePayer.

val pendingTxn =
  aptos
    .signAndSubmitAsFeePayer(
      feePayer = sponsor,
      senderAuthenticator = aliceAuthenticator,
      transaction = txn,
    )
    .expect("Failed to sign and submit as fee payer")