Both the old and new APIs can be used to create transactions, and it is possible to transform a transaction from one format to the other as they share the same representation. However, the focus will shift towards using the new API, while the old API will be deprecated to ensure simplicity, closer alignment with the ledger, and easier maintenance.

In both the new and old APIs, constructing a transaction requires creating a TxBodyContent, along with at least one witness (for example, a ShelleyWitnessSigningKey) to sign the transaction. This process remains unchanged.

To learn how to create a transaction using the old API, see the Cardano.Api.Internal.Tx.Body documentation.

In the examples below, the following qualified modules are used:

import qualified Cardano.Api as Api                -- the general `cardano-api` exports (including the old API)
import qualified Cardano.Api.Script as Script      -- types related to scripts (Plutus and native)
import qualified Cardano.Api.Ledger as Ledger      -- cardano-ledger re-exports
import qualified Cardano.Api.Experimental as Exp   -- the experimental API

For instructions on how to do this, refer to the Test.Cardano.Api.Experimental documentation.

Regardless of whether the experimental or the traditional API is used, creating a TxBodyContent is necessary.

You can see how to do this in the documentation of the Cardano.Api.Internal.Tx.Body module.

If a UTXO has exactly 12 ada, the transaction could be constructed as described in Cardano.Api.Internal.Tx.Body, and it would be valid. However:

• Ada may be wasted
• The UTXO that we intend to spend may not contain exactly 12 ada
• The transaction may not be this simple.

For these reasons, it is recommended to balance the transaction before proceeding with signing and submitting.

For instructions on how to balance a transaction, refer to the Cardano.Api.Internal.Fees documentation.

Signing a transaction requires a witness, such as a ShelleyWitnessSigningKey.

For instructions on creating a ShelleyWitnessSigningKey refer to the Cardano.Api.Internal.Tx.Sign documentation.

This section outlines how to create a transaction using the new API. First, create an UnsignedTx using the makeUnsignedTx function and the Era and TxBodyContent that we defined earlier:

let (Right unsignedTx) = Exp.makeUnsignedTx era txBodyContent

Next, use the key witness to sign the unsigned transaction with the makeKeyWitness function:

let transactionWitness = Exp.makeKeyWitness era unsignedTx (Api.WitnessPaymentKey signingKey)

Finally, sign the transaction using the signTx function:

let newApiSignedTx :: Ledger.Tx (Exp.LedgerEra Exp.ConwayEra) = Exp.signTx era [] [transactionWitness] unsignedTx

The empty list represents the bootstrap witnesses, which are not needed in this case.

The transaction is now signed.

A transaction created with the new API can be easily converted to the old API by wrapping it with the ShelleyTx constructor:

let oldStyleTx :: Api.Tx Api.ConwayEra = ShelleyTx sbe newApiSignedTx

When using a Tx created with the experimental API, the TxBody and TxWits can be extracted using the txBody and txWits lenses from Cardano.Api.Ledger respectively.