Return specific value

post by isha on Jun 21, 2022

Hi all,

When I am trying to make application call contract function returns a value. How do I get that value in a transaction.

This is my code

contract.py

on_result = Seq(
        Assert(
            And(
                Global.latest_timestamp() >= App.globalGet(proposal_start_time),
                Global.latest_timestamp() < App.globalGet(proposal_end_time)
            )
        ),
        If(App.globalGet(yes_count) == App.globalGet(min_num_approval)).Then (
        If(App.globalGet(yes_count) == App.globalGet(total_count)).Then(
            Seq(
                    App.globalPut(vote_result,Int(1)),

)
            )
            .ElseIf(App.globalGet(min_per_approval) >= Btoi(Txn.application_args[2])).Then(
                    (App.globalPut(vote_result,Int(0))),
            )
        ),
        Return (Btoi(vote_result)),

program = Cond(
        [Txn.application_args[0] == Bytes("result"),on_result],
    )
    )

Operations.py(transaction): Need to “vote_result” returned by the on_result call in contract.

def proposal_result(
    client: AlgodClient,
    appID: int,
    proposal_creator: Account,
    proposal_creator_private_key:str,
) -> int:
    suggestedParams = client.suggested_params()

appGlobalState = getAppGlobalState(client, appID)
    appAddr = get_application_address(appID)

quotient = yes_count/total_count
    percentage = quotient * 100

votePercent = int(percentage)
    print ("Converted: ", type(votePercent))

txn = transaction.ApplicationCallTxn(
        sender=proposal_creator,
        index=appID,
        on_complete=transaction.OnComplete.NoOpOC,
        app_args=[b"result",votePercent],
        sp=suggestedParams,
     )

post by fabrice on Jun 21, 2022

Applications can only return 0 to reject the transaction or a non-zero value to accept the transaction via return/Return.

This value is not recorded and just meant to indicate whether the transaction gets recorded or not.

See PyTeal Package — PyTeal documentation

If you want to actually return a value that can be used/read by other applications/the SDK, you need to use the ABI convention:

see step 5 of ARC-4: Algorand Application Binary Interface (ABI)

in other words, you need to log the value prefixed by the four bytes 151f7c75 (these should be the 4 bytes corresponding to the indicated hexadecimal and NOT the 8 bytes “151f7c75”).

post by isha on Jun 22, 2022

Thanks @fabrice this worked!