Call Parameters

When interacting with contracts, you can configure specific parameters for contract calls using the callParams method. The available call parameters are:

1. forward
2. gasLimit

Note: Setting transaction parameters is also available when calling contracts. More information on this can be found at Transaction Parameters.

The contract in use in this section has the following implementation:

impl ReturnContext for Contract {
    #[payable]
    fn return_context_amount() -> u64 {
        msg_amount()
    }
}

See code in context

Forward Parameter

The forward parameter allows the sending of a specific amount of coins to a contract when a function is called. This is useful when a contract function requires coins for its execution, such as paying fees or transferring funds. The forward parameter helps you control the resources allocated to the contract call and offers protection against potentially costly operations.

const amountToForward = 10;

const { waitForResult } = await contract.functions
  .return_context_amount()
  .callParams({
    forward: [amountToForward, provider.getBaseAssetId()],
  })
  .call();

const { value } = await waitForResult();

console.log('forwarded amount:', value.toNumber());
// forwarded amount: 10

See code in context

Gas Limit Parameter

The gasLimit refers to the maximum amount of gas that can be consumed specifically by the contract call itself, separate from the rest of the transaction.

try {
  await contract.functions
    .return_context_amount()
    .callParams({
      forward: [10, provider.getBaseAssetId()],
      gasLimit: 1,
    })
    .call();
} catch (e) {
  console.log('error', e);
  // error _FuelError: The transaction reverted with reason: "OutOfGas"
}

See code in context

Call Parameter gasLimit vs Transaction Parameter gasLimit

The call parameter gasLimit sets the maximum gas allowed for the actual contract call, whereas the transaction parameter gasLimit (see Transaction Parameters) sets the maximum gas allowed for the entire transaction and constrains the gasLimit call parameter. If the call parameter gasLimit is set to a value greater than the available transaction gas, then the entire available transaction gas will be allocated for the contract call execution.

If you don't set the gasLimit for the call, the transaction gasLimit will be applied.

Setting Both Parameters

You can set both call parameters and transaction parameters within the same contract function call.

const contractCallGasLimit = 4_000;
const transactionGasLimit = 100_000;

const { waitForResult } = await contract.functions
  .return_context_amount()
  .callParams({
    forward: [10, provider.getBaseAssetId()],
    gasLimit: contractCallGasLimit,
  })
  .txParams({
    gasLimit: transactionGasLimit,
  })
  .call();

See code in context