`Integer` as `Datum` in offchain code

Question

In the onchain validator I used Integer type for Datum and everything was fine but when I want to use mustPayToOtherScript tx constraint in the offchain code I get the following error:

 • Couldn't match expected type ‘Datum’ with actual type ‘Integer’
 • In the second argument of ‘mustPayToOtherScript’

Edit: offchain code

start :: AsContractError e => Promise () OwnerSchema e ()
start = endpoint @"start" $ \const -> do
    pkh <- pubKeyHash <$> ownPubKey
    let 
        tokenAAmount = 10000000000 
        tokenBAmount = 1000000000000
        lt = 100000000000
        value = (V.assetClassValue poolNFT 1) <>
                (V.assetClassValue tokenA tokenAAmount) <>
                (V.assetClassValue tokenB tokenBAmount)
        tx   = mustPayToTheScript (lt) value 
    ledgerTx <- submitTxConstraints poolInst' tx
    void $ awaitTxConfirmed $ txId ledgerTx
    void $ waitNSlots 1
    logInfo @String $ printf "created pool UTXO %s at validator hash %s" (show poolParams) (show $ orderBoxVH')
    return ()

Answer 1

Your off-chain code is using mustPayToTheScript and not mustPayToOtherScript. It's important to note the difference, since mustPayToTheScript will require a datum with the type you defined in poolInst', while mustPayToOtherScript will require a datum of type Datum.

So, I will assume you want to use the latter. In this case, you need to convert your variable of type Integer to a variable of type Datum. This can be easily done with (Datum $ PlutusTx.toBuiltinData lt).

Assuming your logic and other components are working, your code would look like the following:

start :: AsContractError e => Promise () OwnerSchema e ()
start = endpoint @"start" $ \const -> do
    pkh <- pubKeyHash <$> ownPubKey
    let 
        tokenAAmount = 10000000000 
        tokenBAmount = 1000000000000
        lt = 100000000000
        value = (V.assetClassValue poolNFT 1) <>
                (V.assetClassValue tokenA tokenAAmount) <>
                (V.assetClassValue tokenB tokenBAmount)
        tx   = mustPayToOtherScript (Datum $ PlutusTx.toBuiltinData lt) value 
    ledgerTx <- submitTxConstraints poolInst' tx
    void $ awaitTxConfirmed $ txId ledgerTx
    void $ waitNSlots 1
    logInfo @String $ printf "created pool UTXO %s at validator hash %s" (show poolParams) (show $ orderBoxVH')
    return ()

Just so it gets easy to debug in the future, I would suggest you to create a function focused specifically in the contract and another function for handling endpoints.