Transaction Builder#

The TxBuilder class tries to reduces the complexity of creating a transaction to a minimum. The objective is to empower everyone to create their own transactions.

The class arguments will be explained inside the class itself. But an example with explanation can be read below.

The TxBuilder, as well as the whole implementation, supports building transactions for all address types (P2PKH, P2SH, P2WPKH) currently supported by defichain. Both networks, mainnet and testnet, are supported.

Assumptions

Because of the reduced the complexity when using the TxBuilder some assumptions had to be made:

  • All UTXO inputs of an address will be used and combined to one UTXO output (unless otherwise stated in the method)

  • When executing a DefiTx the UTXO outputs will always go back to the same address

TxBuilder Modules#

Example with explanation#

The following example demonstrates how to create, sign, and send a transaction to the defichain network using the TxBuilder object:

# 1. Import ocean, wallet, txbuilder and the network
from defichain import Ocean, Wallet, TxBuilder
from defichain.networks import DefichainMainnet

# 2. Specify ocean connection
ocean =  Ocean(network="mainnet")

# 3. Create wallet and account
mnemonic = "avocado key fan step egg engage winter upper attitude carry regret mixed utility body party trip valid oppose gas ensure deputy suspect blur trade"

wallet = Wallet(DefichainMainnet)
wallet.from_mnemonic(mnemonic)

account = wallet.get_account(0)

# 4. Create TxBuilder
builder = TxBuilder(account.get_p2wpkh(), account, ocean)

addressFrom = account.get_p2wpkh()
tokenFrom = "BTC"
amount = 0.1
addressTo = account.get_p2wpkh()
tokenTo = "DFI"
maxprice = 3000

# 5. Build poolswap transaction
tx = builder.pool.poolswap(addressFrom, tokenFrom, amount, addressTo, tokenTo, maxprice)

# 6. Send transaction into the blockchain
txid = builder.send_tx(tx)

# 7. Print txid
print(txid)

Initialization of the TxBuilder object#

The following four steps must always be fulfilled at the beginning of a new project / script to create a TxBuilder object:

  1. First, all the necessary elements required for creating transactions must be imported. This includes a connection to Ocean, the Wallet Implementation, and the TxBuilder object itself. Since this example pertains to building transactions for the mainnet, the correct network must be imported.

  2. In the second step, the ocean object is initialized, establishing a connection to the Ocean mainnet. This connection is necessary because certain information from the blockchain are required to create a transaction. These details do not necessarily have to come from Ocean; you can also use a connection to your own defichain node or manually input the required information.

  3. In the third step, the account being used must be initialized. In the example, a wallet is initialized using a mnemonic seed, and from that seed, the first account is derived. This is similar to using the first address in the LightWallet. However, the account object can also be initialized directly using the private key.

  4. As the fourth step, the TxBuilder object is initialized with the dependencies created earlier. Since an account represents exactly one private key, which in turn corresponds to three different address types (P2PKH, P2SH, P2WPKH), the appropriate address must be provided as the first argument.

Creating, signing, and sending transactions#

The following three steps are based on the previously created TxBuilder object.

  1. In this code line, the actual transaction is created and automatically signed using the TxBuilder object. In this example, a poolswap transaction is shown. Creating transactions closely follows the arguments known by the defichain node. All implemented transaction types and their arguments can be found in the documentation.

  2. Once the transaction is created and signed, it can be added to the defichain network using the TxBuilder object as well.

  3. If the transaction is valid and accepted by the blockchain, a transaction hash is returned.