from token transaction detail, how can I know if token is actually transferred?

Question

I am implementing support of multiple tokens in my application. I want to listen new token received transactions.

I got that I need to decode the input data in any transaction to get the toAddress and Amount of token transferred. But I am confused at a point how can I know if token is really transferred or not? because method in input data can be different for different contracts.

So I know that transfer, transferFrom are methods used to transfer the token. so I can confirm if token-transfer is happened. But I found Transfer and Sweep two methods for a contract. (for eg. Omisego Contract, Omisego Transaction-1, Omisego Transaction). but then I found depositToken method for another contract(for eg. Sharder Contract Sharder Transaction).

So my questions.

1. How can I get a list of transfer-methods for different tokens?(for eg. transfer-transferFrom for Omisego, depositToken for Sharder etc..)
2. is Mint method too a type of token transfer method, its here Omisego Contract?
3. or may be, if transaction is on Etherscan, assume tokens/ETH are always transferred from one address to another address/contract.

Thanks in advance for the help.

Answer 1

This is exactly what standards are meant for. Without a standard it's next to impossible to know what functions are supposed to do what and which tokens support which functionality.

The best-known token stardard is ERC20 which defines the function names and some other stuff. If a token does not follow that standard it isn't a valid ERC20 token.

You can't really assume anything with contracts which are not ERC20 compliant. They may do whatever they wish with whatever functions.

Strictly speaking, nobody guarantees that a ERC20 contract transfers tokens with a transfer function either as the implementation is not built-in, so you still have to make other checks to make sure (check token balances before and after).