Struct bdk::wallet::tx_builder::TxBuilder

pub struct TxBuilder<'a, B, D, Cs, Ctx> { /* fields omitted */ }

A transaction builder

A TxBuilder is created by calling build_tx or build_fee_bump on a wallet. After assigning it, you set options on it until finally calling finish to consume the builder and generate the transaction.

Each option setting method on TxBuilder takes and returns &mut self so you can chain calls as in the following example:

// chaining
let (psbt1, details) = {
    let mut builder = wallet.build_tx();
    builder
       .ordering(TxOrdering::Untouched)
       .add_recipient(addr1.script_pubkey(), 50_000)
       .add_recipient(addr2.script_pubkey(), 50_000);
    builder.finish()?
};

// non-chaining
let (psbt2, details) = {
    let mut builder = wallet.build_tx();
    builder.ordering(TxOrdering::Untouched);
    for addr in &[addr1, addr2] {
        builder.add_recipient(addr.script_pubkey(), 50_000);
    }
    builder.finish()?
};

assert_eq!(psbt1.global.unsigned_tx.output[..2], psbt2.global.unsigned_tx.output[..2]);

At the moment coin_selection is an exception to the rule as it consumes self. This means it is usually best to call coin_selection on the return value of build_tx before assigning it.

For further examples see this module's documentation;

Implementations

impl<'a, B, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext> TxBuilder<'a, B, D, Cs, Ctx>

pub fn fee_rate(&mut self, fee_rate: FeeRate) -> &mut Self

Set a custom fee rate

pub fn fee_absolute(&mut self, fee_amount: u64) -> &mut Self

Set an absolute fee

pub fn policy_path(
    &mut self,
    policy_path: BTreeMap<String, Vec<usize>>,
    keychain: KeychainKind
) -> &mut Self

Set the policy path to use while creating the transaction for a given keychain.

This method accepts a map where the key is the policy node id (see Policy::id) and the value is the list of the indexes of the items that are intended to be satisfied from the policy node (see SatisfiableItem::Thresh::items).

Example

An example of when the policy path is needed is the following descriptor: wsh(thresh(2,pk(A),sj:and_v(v:pk(B),n:older(6)),snj:and_v(v:pk(C),after(630000)))), derived from the miniscript policy thresh(2,pk(A),and(pk(B),older(6)),and(pk(C),after(630000))). It declares three descriptor fragments, and at the top level it uses thresh() to ensure that at least two of them are satisfied. The individual fragments are:

1. pk(A)
2. and(pk(B),older(6))
3. and(pk(C),after(630000))

When those conditions are combined in pairs, it's clear that the transaction needs to be created differently depending on how the user intends to satisfy the policy afterwards:

• If fragments 1 and 2 are used, the transaction will need to use a specific n_sequence in order to spend an OP_CSV branch.
• If fragments 1 and 3 are used, the transaction will need to use a specific locktime in order to spend an OP_CLTV branch.
• If fragments 2 and 3 are used, the transaction will need both.

When the spending policy is represented as a tree (see Wallet::policies), every node is assigned a unique identifier that can be used in the policy path to specify which of the node's children the user intends to satisfy: for instance, assuming the thresh() root node of this example has an id of aabbccdd, the policy path map would look like:

{ "aabbccdd" => [0, 1] }

where the key is the node's id, and the value is a list of the children that should be used, in no particular order.

If a particularly complex descriptor has multiple ambiguous thresholds in its structure, multiple entries can be added to the map, one for each node that requires an explicit path.

let mut path = BTreeMap::new();
path.insert("aabbccdd".to_string(), vec![0, 1]);

let builder = wallet.build_tx()
    .add_recipient(to_address.script_pubkey(), 50_000)
    .policy_path(path, KeychainKind::External);

pub fn add_utxos(&mut self, outpoints: &[OutPoint]) -> Result<&mut Self, Error>

Add the list of outpoints to the internal list of UTXOs that must be spent.

If an error occurs while adding any of the UTXOs then none of them are added and the error is returned.

These have priority over the "unspendable" utxos, meaning that if a utxo is present both in the "utxos" and the "unspendable" list, it will be spent.

pub fn add_utxo(&mut self, outpoint: OutPoint) -> Result<&mut Self, Error>

Add a utxo to the internal list of utxos that must be spent

These have priority over the "unspendable" utxos, meaning that if a utxo is present both in the "utxos" and the "unspendable" list, it will be spent.

pub fn manually_selected_only(&mut self) -> &mut Self

Only spend utxos added by add_utxo.

The wallet will not add additional utxos to the transaction even if they are needed to make the transaction valid.

pub fn unspendable(&mut self, unspendable: Vec<OutPoint>) -> &mut Self

Replace the internal list of unspendable utxos with a new list

It's important to note that the "must-be-spent" utxos added with TxBuilder::add_utxo have priority over these. See the docs of the two linked methods for more details.

pub fn add_unspendable(&mut self, unspendable: OutPoint) -> &mut Self

Add a utxo to the internal list of unspendable utxos

It's important to note that the "must-be-spent" utxos added with TxBuilder::add_utxo have priority over this. See the docs of the two linked methods for more details.

pub fn sighash(&mut self, sighash: SigHashType) -> &mut Self

Sign with a specific sig hash

Use this option very carefully

pub fn ordering(&mut self, ordering: TxOrdering) -> &mut Self

Choose the ordering for inputs and outputs of the transaction

pub fn nlocktime(&mut self, locktime: u32) -> &mut Self

Use a specific nLockTime while creating the transaction

This can cause conflicts if the wallet's descriptors contain an "after" (OP_CLTV) operator.

pub fn version(&mut self, version: i32) -> &mut Self

Build a transaction with a specific version

The version should always be greater than 0 and greater than 1 if the wallet's descriptors contain an "older" (OP_CSV) operator.

pub fn do_not_spend_change(&mut self) -> &mut Self

Do not spend change outputs

This effectively adds all the change outputs to the "unspendable" list. See TxBuilder::unspendable.

pub fn only_spend_change(&mut self) -> &mut Self

Only spend change outputs

This effectively adds all the non-change outputs to the "unspendable" list. See TxBuilder::unspendable.

pub fn change_policy(&mut self, change_policy: ChangeSpendPolicy) -> &mut Self

Set a specific ChangeSpendPolicy. See TxBuilder::do_not_spend_change and TxBuilder::only_spend_change for some shortcuts.

pub fn force_non_witness_utxo(&mut self) -> &mut Self

Fill-in the psbt::Input::non_witness_utxo field even if the wallet only has SegWit descriptors.

This is useful for signers which always require it, like Trezor hardware wallets.

pub fn include_output_redeem_witness_script(&mut self) -> &mut Self

Fill-in the psbt::Output::redeem_script and psbt::Output::witness_script fields.

This is useful for signers which always require it, like ColdCard hardware wallets.

pub fn add_global_xpubs(&mut self) -> &mut Self

Fill-in the PSBT_GLOBAL_XPUB field with the extended keys contained in both the external and internal descriptors

This is useful for offline signers that take part to a multisig. Some hardware wallets like BitBox and ColdCard are known to require this.

pub fn drain_wallet(&mut self) -> &mut Self

Spend all the available inputs. This respects filters like TxBuilder::unspendable and the change policy.

pub fn coin_selection<P: CoinSelectionAlgorithm<D>>(
    self,
    coin_selection: P
) -> TxBuilder<'a, B, D, P, Ctx>

Choose the coin selection algorithm

Overrides the DefaultCoinSelectionAlgorithm.

Note that this function consumes the builder and returns it so it is usually best to put this as the first call on the builder.

pub fn finish(self) -> Result<(PSBT, TransactionDetails), Error>

Finish the building the transaction.

Returns the BIP174 "PSBT" and summary details about the transaction.

impl<'a, B, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>> TxBuilder<'a, B, D, Cs, CreateTx>

pub fn set_recipients(&mut self, recipients: Vec<(Script, u64)>) -> &mut Self

Replace the recipients already added with a new list

pub fn add_recipient(&mut self, script_pubkey: Script, amount: u64) -> &mut Self

Add a recipient to the internal list

pub fn set_single_recipient(&mut self, recipient: Script) -> &mut Self

Set a single recipient that will get all the selected funds minus the fee. No change will be created

This method overrides any recipient set with set_recipients or add_recipient.

It can only be used in conjunction with drain_wallet to send the entire content of the wallet (minus filters) to a single recipient or with a list of manually selected UTXOs by enabling manually_selected_only and selecting them with or add_utxo.

When bumping the fees of a transaction made with this option, the user should remeber to add maintain_single_recipient to correctly update the single output instead of adding one more for the change.

pub fn enable_rbf(&mut self) -> &mut Self

Enable signaling RBF

This will use the default nSequence value of 0xFFFFFFFD.

pub fn enable_rbf_with_sequence(&mut self, nsequence: u32) -> &mut Self

Enable signaling RBF with a specific nSequence value

This can cause conflicts if the wallet's descriptors contain an "older" (OP_CSV) operator and the given nsequence is lower than the CSV value.

If the nsequence is higher than 0xFFFFFFFD an error will be thrown, since it would not be a valid nSequence to signal RBF.

impl<'a, B, D: BatchDatabase> TxBuilder<'a, B, D, DefaultCoinSelectionAlgorithm, BumpFee>

pub fn maintain_single_recipient(&mut self) -> Result<&mut Self, Error>

Bump the fees of a transaction made with set_single_recipient

Unless extra inputs are specified with add_utxo, this flag will make bump_fee reduce the value of the existing output, or fail if it would be consumed entirely given the higher new fee rate.

If extra inputs are added and they are not entirely consumed in fees, a change output will not be added; the existing output will simply grow in value.

Fails if the transaction has more than one outputs.

Trait Implementations

impl<'a, B: Clone, D: Clone, Cs: Clone, Ctx: Clone> Clone for TxBuilder<'a, B, D, Cs, Ctx>

fn clone(&self) -> TxBuilder<'a, B, D, Cs, Ctx>

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a, B: Debug, D: Debug, Cs: Debug, Ctx: Debug> Debug for TxBuilder<'a, B, D, Cs, Ctx>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.