Custom Transactions

There may be scenarios where you need to build out transactions that involve multiple program types and assets; this can be done by instantiating a ScriptTransactionRequest. This class allows you to a append multiple program types and assets to a single transaction.

Consider the following script that transfers multiple assets to a contract:

script;

use std::asset::transfer;

fn main(
    contract_address: b256,
    asset_a: AssetId,
    amount_asset_a: u64,
    asset_b: AssetId,
    amount_asset_b: u64,
) -> bool {
    let wrapped_contract = ContractId::from(contract_address);
    let contract_id = Identity::ContractId(wrapped_contract);
    transfer(contract_id, asset_a, amount_asset_a);
    transfer(contract_id, asset_b, amount_asset_b);
    true
}

See code in context

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This script can be executed by creating a ScriptTransactionRequest, appending the resource and contract inputs/outputs and then sending the transaction, as follows:

// 1. Create a script transaction using the script binary
const request = new ScriptTransactionRequest({
  ...defaultTxParams,
  gasLimit: 3_000_000,
  script: ScriptTransferToContract.bytecode,
});

// 2. Instantiate the script main arguments
const scriptArguments = [
  contract.id.toB256(),
  { bits: ASSET_A },
  new BN(1000),
  { bits: ASSET_B },
  new BN(500),
];

// 3. Populate the script data and add the contract input and output
request
  .setData(ScriptTransferToContract.abi, scriptArguments)
  .addContractInputAndOutput(contract.id);

// 4. Get the transaction resources
const quantities = [coinQuantityfy([1000, ASSET_A]), coinQuantityfy([500, ASSET_B])];

// 5. Calculate the transaction fee
const txCost = await wallet.getTransactionCost(request, { quantities });

request.gasLimit = txCost.gasUsed;
request.maxFee = txCost.maxFee;

await wallet.fund(request, txCost);

// 6. Send the transaction
const tx = await wallet.sendTransaction(request);
await tx.waitForResult();

const contractFinalBalanceAssetA = await contract.getBalance(ASSET_A);
const contractFinalBalanceAssetB = await contract.getBalance(ASSET_B);

console.assert(new BN(contractFinalBalanceAssetA).toNumber() === 1000, 'unexpected balance');
console.assert(new BN(contractFinalBalanceAssetB).toNumber() === 500, 'unexpected balance');

See code in context

Full Example

For a full example, see below:

import { BN, ScriptTransactionRequest, coinQuantityfy } from 'fuels';
import { ASSET_A, ASSET_B, launchTestNode } from 'fuels/test-utils';

import { EchoValuesFactory } from '../typegend/contracts/EchoValuesFactory';
import { ScriptTransferToContract } from '../typegend/scripts/ScriptTransferToContract';

using launched = await launchTestNode({
  contractsConfigs: [{ factory: EchoValuesFactory }],
});
const {
  contracts: [contract],
  wallets: [wallet],
} = launched;

const defaultTxParams = {
  gasLimit: 10000,
};


// 1. Create a script transaction using the script binary
const request = new ScriptTransactionRequest({
  ...defaultTxParams,
  gasLimit: 3_000_000,
  script: ScriptTransferToContract.bytecode,
});

// 2. Instantiate the script main arguments
const scriptArguments = [
  contract.id.toB256(),
  { bits: ASSET_A },
  new BN(1000),
  { bits: ASSET_B },
  new BN(500),
];

// 3. Populate the script data and add the contract input and output
request
  .setData(ScriptTransferToContract.abi, scriptArguments)
  .addContractInputAndOutput(contract.id);

// 4. Get the transaction resources
const quantities = [coinQuantityfy([1000, ASSET_A]), coinQuantityfy([500, ASSET_B])];

// 5. Calculate the transaction fee
const txCost = await wallet.getTransactionCost(request, { quantities });

request.gasLimit = txCost.gasUsed;
request.maxFee = txCost.maxFee;

await wallet.fund(request, txCost);

// 6. Send the transaction
const tx = await wallet.sendTransaction(request);
await tx.waitForResult();

const contractFinalBalanceAssetA = await contract.getBalance(ASSET_A);
const contractFinalBalanceAssetB = await contract.getBalance(ASSET_B);

console.assert(new BN(contractFinalBalanceAssetA).toNumber() === 1000, 'unexpected balance');
console.assert(new BN(contractFinalBalanceAssetB).toNumber() === 500, 'unexpected balance');

See code in context