Identify token transfer in transaction

[0x-j]

Asked by sly_of_zero on discord

how to identify if a transaction was a token transfer? I need to know the token being transferred, the amount of the token, and the receiver

[0x-j]

I assume you are talking about transferring coin (ERC-20 on Aptos), you can find these info in the event of the tx. Here's an example where I transfer APT to another account. It had one 0x1::coin::WithdrawEvent that withdrew APT from my wallet, and one 0x1::coin::DepositEvent that deposited to the recipient.

[slyofzero]

So my purpose of keeping track of this is to make something like a buybot which tracks any token buys. Would these events mark any token transfer from one address to another? In this case I should be listening for any 0x1::coin::DepositEvent?

[gregnazario]

0x1::coin::DepositEvent will tell you when someone deposits tokens to their account.

0x1::coin::WithdrawEvent will tell you when someone removes tokens from their account.

In the case of buys or transfers, you will always have a deposit on the user who receives the token, and a withdrawal from the other user. It is possible if the coins don't go through the CoinStore that no withdraw event is emitted

Here's a more detailed doc on how to track coin events https://aptos.dev/guides/system-integrators-guide/#tracking-coin-balance-changes