Fuels-ts

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Script With Configurable ​

In the same way as contracts and predicates, Scripts also support configurable constants. This feature enables dynamic adjustment of certain values within your scripts.

Configurable constants are fairly straightforward to add and set in your scripts.

Let's consider the following script:

rust
script;

configurable {
    AMOUNT: u32 = 10,
}

fn main(inputted_amount: u32) -> u32 {
    inputted_amount + AMOUNT
}
See code in context

In this script, AMOUNT is a configurable constant with a default value of 10. The main function returns the sum of the inputted_amount and the configurable constant AMOUNT.

To change the value of the AMOUNT constant, we can use the setConfigurableConstants method as shown in the following example:

ts
const provider = await Provider.create(LOCAL_NETWORK_URL);
const wallet = Wallet.fromPrivateKey(WALLET_PVT_KEY, provider);
const script = new Script(ScriptSum.bytecode, ScriptSum.abi, wallet);

const configurableConstants = {
  AMOUNT: 81,
};

script.setConfigurableConstants(configurableConstants);

const inputtedValue = 10;

const { waitForResult } = await script.functions.main(inputtedValue).call();
const { value } = await waitForResult();

const expectedTotal = inputtedValue + configurableConstants.AMOUNT;

console.assert(new BN(value as number).toNumber() === expectedTotal, 'unexpected total');
See code in context

In this example, we're setting a new value 81 for the AMOUNT constant. We then call the main function with an inputted value of 10.

The expectation is that the script will return the sum of the inputted value and the new value of AMOUNT.

This way, configurable constants in scripts allow for more flexibility and dynamic behavior during execution.

Full Example ​

For a full example, see below:

ts
import { Script, BN, Wallet, Provider } from 'fuels';

import { WALLET_PVT_KEY, LOCAL_NETWORK_URL } from '../env';
import { ScriptSum } from '../typegend/scripts/ScriptSum';

const provider = await Provider.create(LOCAL_NETWORK_URL);
const wallet = Wallet.fromPrivateKey(WALLET_PVT_KEY, provider);
const script = new Script(ScriptSum.bytecode, ScriptSum.abi, wallet);

const configurableConstants = {
  AMOUNT: 81,
};

script.setConfigurableConstants(configurableConstants);

const inputtedValue = 10;

const { waitForResult } = await script.functions.main(inputtedValue).call();
const { value } = await waitForResult();

const expectedTotal = inputtedValue + configurableConstants.AMOUNT;

console.assert(new BN(value as number).toNumber() === expectedTotal, 'unexpected total');

const argument = 10;
const expected = 20;

const myMainScript = new Script(ScriptSum.bytecode, ScriptSum.abi, wallet);

const tx = myMainScript.functions.main(argument);

// Set the call parameters
tx.callParams({ gasLimit: 1500 });

// Get the entire transaction request prior to
const txRequest = await tx.getTransactionRequest();

// Get the transaction ID
const txId = await tx.getTransactionId();

// Retrieve the value of the call and the actual gas used
const { waitForResult: waitForActualGasUsed } = await tx.call();
const { value: valueOfActualGasUsed, gasUsed: gasUsedOfActualGasUsed } =
  await waitForActualGasUsed();
console.assert(txRequest, 'txn request undefined');
console.assert(txId, 'txn id undefined');
console.assert(new BN(valueOfActualGasUsed as number).toNumber() === expected, 'unexpected total');
console.assert(new BN(gasUsedOfActualGasUsed).toNumber() > 0, 'gas used is 0');
See code in context