How can I sign & send multiple transactions at once? Batch transactions

[adriandelgg]

Hi, I want to be able to send 2 transactions in 1 transaction.

How can I do this?

Example:

1. I want to approve ERC20 tokens to a spender. approve()
2. I want to send my tokens to a contract transferFrom()

[htadashi]

Hi adiandelgg. You can deploy a contract that will work as a "smart wallet" and use a for-loop with delegate call to batch N transactions in a single transaction. For instance, in DeFi Basket we deploy this contract for our users and use the function useBridges to batch the calls. You can see how we use ethers to batch transactions to this contract in these test examples. Another useful reference is DS Proxy contracts.

P.S.: Be aware that using this pattern has some security issues. For example, you should use delegate call only to call trusted contracts, and in case you make useBridges payable, take care to not use msg.value in a wrong way.