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ethereumsolidity

Is it safe to read the ethereum smart contract balance directly to calculate the transfer of assets to users?

I have contract, through which users can trade on DEX.

Like this:

// transfer asset A from msg.sender 
ERC20(AToken).transferFrom(msg.sender, address(this), amount);


// do trade A to B 
... trade logic here 


// get balance of asset B after trade 
// asset B after trade gets to this contract address
uint256 returnAmount = ERC20(BToken).balanceOf(address(this));


// transfer asset B to msg.sender 
ERC20(BToken).transfer(msg.sender, returnAmount);

I wonder about returnAmount, is this logic safe?

Transactions in ethereum are performed either completely or not performed at all, and also in order of priority.

But I’m still wondering if there could be such a case when returnAmount shows incorrectly, for example, contract get the balance after the transaction of another user?

Solution

  • Transactions in ETH are executed one by one, other transactions can not interfere to execution of a transaction when it's running by EVM.