How to check if a transaction has completed correctly or has been rejected by some assert check

Question

We have developed a simple Smart Contract which offers this following public transaction method:

function bid(uint256 _userCode, uint256 _amount) public {

        assert(_userCode> 0);
        assert(_amount> 0);

        winningBid.userCode= _userCode;
        winningBid.amount= _amount;

        var bidData= Bid(_userCode, _amount);
        bids.push(bidData);
    }

We are sending the transaction using this Nethereum code:

var result = bidFunction.SendTransactionAndWaitForReceiptAsync(address, gas, balance, null, userCode, amount).Result;

The method invocation does not throw any exception, even passing 0 to the userCode that, if you take a look to the Smart Contract, should trigger the assert and stop the method execution.

How could we check if a transaction has completed correctly or has been rejected by some assert check?

Does the function include a parameter for a callback function? This is usually how it is done. — jojeyh, Nov 24 '17 at 13:22
We are not using any callback function. Could you please provide an example? — systempuntoout, Nov 24 '17 at 13:24
Since byzantinum the recipt includes a field status to indicate if the transaction was executed correctly or not. — Ismael, Nov 25 '17 at 04:25

score 0 · Answer 1 · answered Nov 24 '17 at 16:01

Reading the Solidity docs on error handling, these things come to mind:

You should use require instead of assert. Assert is for detecting bugs in the code. Require is for aborting operation on invalid input (your use case).
Solidity will revert the whole operation, when it encounters assert or require and nothing will be changed.
Catching exceptions is not yet possible.

You could make your function return the accepted value, e.g.:

function bid(uint256 _userCode, uint256 _amount) public constant returns (uint256) {

    assert(_userCode> 0);
    assert(_amount> 0);

    winningBid.userCode= _userCode;
    winningBid.amount= _amount;

    var bidData= Bid(_userCode, _amount);
    bids.push(bidData);

    return _amount;
}

It should be possible to tell the difference between a successful call and a failed one, right?

Thanks for your answer. Since the bid function is a transaction (it's changing the blockchain state) you can't read the transaction return value via Nethereum SDK; all you can get is a receipt. — systempuntoout, Nov 24 '17 at 16:10

How to check if a transaction has completed correctly or has been rejected by some assert check

1 Answers1