Ethersjs: check that a transaction method in contract emitted an event

Question

I have a contract with the getOwnerAddress function that emits a OwnerReturned event:

...
function getOwnerAddress() external returns (address) {
    emit OwnerReturned("Owner");
    return owner;
}
event OwnerReturned(string message);
...

I'm trying to check whether a transaction emitted an OwnerReturned event:

let ownerTransaction = await contract.getOwnerAddress({
    nonce:  await signer.getNonce()
});
let ownerResult = await ownerTransaction.wait();
let ownerEvents = ownerResult.events;
if (ownerEvents !== undefined)  {
    let ownerReturnedEvent = ownerEvents.find(e => e.event === 'Owner');
    console.log(ownerReturnedEvent);
} else  {
    console.log("Undefined events!");
}

The transaction executes, however the ownerEvents is undefined.

Am I doing something wrong? How do I check if the transaction had OwnerReturned event emitted?

Answer 1

If you're using ethers.js ^= v6, the issue is no surprise.

You'd need to access the logs property of the transaction receipt for reading the events that were emitted during the transaction execution.

Like this:

tx = await connectedToken.transfer(receiver.address, amount)
result = await tx.wait()
console.log('transaction events', result.logs);

---

In your particular case, it's equivalent to the following code snippet:

let ownerTransaction = await contract.getOwnerAddress({
    nonce:  await signer.getNonce()
});
let ownerResult = await ownerTransaction.wait();
let ownerEvents = ownerResult.logs;

if (ownerEvents !== undefined)  {
    let ownerReturnedEvent = ownerEvents.find(e => e.topics[0] === 'Owner');
    console.log(ownerReturnedEvent);
} else  {
    console.log("Undefined events!");
}

txReceipt.logs is an array readonly Log[] (https://docs.ethers.org/v6/api/providers/#Log)