How do I send multiple transactions as one transaction?

Question

Say I need a user to approve a contract with an erc20 token balance and then the contract can execute it's function after. Typically, I would have to do an approve transaction with a nonce of 1 and then call the contract after that with a nonce of 2.

This means that we have to wait at least two blocks before the total of the two transactions complete.

How can I send these transactions at the same time, and included in the same block while still ensuring the ordering of their execution?

It might look something like this:

await sendTransactions([
    token.approve(myContract, toWei('1000000')), // Gets executed in the same block before someFunction
    myContract.someFunction() // Gets executed in the same block after approve function
]);

Answer 1

Do you know the MultiSender app?

It allows for multiple Ether and ERC 20 token transactions to be bundled in one transaction. It's open-source on Github rstormsf/multisender in case you want to review the logic.

There's also a more detailled write-up on Medium: MultiSender — Send Ether and Ethereum Tokens to Multiple Ethereum Addresses In A Single Transaction.