Create examples for retrieving payFees for a transaction and for dry-run executions

[johandroid]

Hello team,

Can you please include some examples for:

• Retrieving payFees for a transaction
• Execute dry-run executions

I have been checking the docs, but it's not correct, it looks like subxt::rpc module is the one to be used but it's not there

It looks like the real rpc methods are in subxt::backend::legacy::rpc_methods

Thank you

[jsdw]

Hello!

This (untested but hopefully correct!) example shows how to validate (dry run) the transaction and get an estimate of the fees it'll cost; is this what you're after?:

use subxt::{OnlineClient, PolkadotConfig};
use subxt_signer::sr25519::dev;

#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale")]
pub mod polkadot {}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {

    let api = OnlineClient::<PolkadotConfig>::new().await?;

    // Build the balance transfer call data.
    let dest = dev::bob().public_key().into();
    let balance_transfer_tx = polkadot::tx().balances().transfer_allow_death(dest, 10_000);

    // Create a transaction ready to submit
    let from = dev::alice();
    let submittable_tx = api
        .tx()
        .create_signed(&balance_transfer_tx, &from, Default::default())
        .await?;

    // Validate it via TaggedTransactionQueue_validate_transaction:
    let validation_result = submittable_tx.validate().await?;

    // Get an estimate of the fees needed for it via TransactionPaymentApi_query_info 
    // (less any tips added, here we added none anyway). This amount can vary based 
    // on node traffic etc so is not guaranteed:
    let fee_estimate = submittable_tx.partial_fee_estimate().await;

    Ok(())
}