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Context

I was looking for a simple way to get exact TxOut on on-chain code to validate if funds are to be unlocked to correct wallet address. While looking in plutus haddoc I have found this function:

{-# INLINABLE findOwnInput #-}
-- | Find the input currently being validated.
findOwnInput :: ScriptContext -> Maybe TxInInfo
findOwnInput ScriptContext{scriptContextTxInfo=TxInfo{txInfoInputs}, scriptContextPurpose=Spending txOutRef} =
    find (\TxInInfo{txInInfoOutRef} -> txInInfoOutRef == txOutRef) txInfoInputs
findOwnInput _ = Nothing

This function returns:

-- | An input of a pending transaction.
data TxInInfo = TxInInfo
    { txInInfoOutRef   :: TxOutRef
    , txInInfoResolved :: TxOut
    } deriving stock (Generic, Haskell.Show, Haskell.Eq)

And here is where most of my confusion comes from - getOwnInput returns TxInInfo which has TxOut. All I see is TxIn is TxOut. This makes it really unclear to me exactly which part of locking or unlocking transaction UTXO getOwnInput function returns.

Lets say that I have 10 Ada in wallet A and I'm creating locking transaction TX1 of 2 Ada to SC1. The way I see it TX1 should look like this:

  1. UTXO1 of 10 ADA is created by taking all the funds from wallet A.
  2. UTXO2 of 10 ADA - 2 ADA - fees1 is created and is sent back to wallet A.
  3. UTXO3 of 2 ADA is created and sent to SC1.

Lets say that now I'm trying to unlock 2 ADA from SC1 back to wallet A by creating TX2:

  1. UTXO4 10 ADA - 2 ADA - fees1 are taken from wallet A to pay for fees2
  2. UTXO5 2 ADA is being taken from SC1
  3. UTXO6 2 ADA are sent to wallet A
  4. UTXO7 10 ADA - 2 ADA - fees1 - fees2 are sent back to wallet A

Main question

So my main question is. Which of these UTXOs does the function getOwnInput return as a txInInfoResolved when TX2 is created?

Bonus question

When TX2 is created, from Plutus validator point of view, which of UTXOs are TxOut and which are TxIn?

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  • My guess would be that answer to main question is UTXO3, because on this tx pubKeyOutput returns Nothing. I suppose it is because UTXO3 goes into smartcontract which doesn't have PubKeyHash but has ValidatorHash instead.
    – KugisMugis
    Jan 27 at 10:16

1 Answer 1

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Calling findOwnInput in a validator returns the value contained in the Script-UTxO that is currently being validated. In your example above it is the one with 2 Ada in it.

Your example above is, however, not correctly formulated: UTXO4 is in fact UTXO2 and UTXO5 is UTXO3, also UTXO7 and UTXO4 are not necessary.

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