blocks_subscribing.rs

#![allow(missing_docs)]
use subxt::{OnlineClient, PolkadotConfig};

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

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a client to use:
    let api = OnlineClient::<PolkadotConfig>::new().await?;

    // Subscribe to all finalized blocks:
    let mut blocks_sub = api.blocks().subscribe_finalized().await?;

    // For each block, print a bunch of information about it:
    while let Some(block) = blocks_sub.next().await {
        let block = block?;

        let block_number = block.header().number;
        let block_hash = block.hash();

        println!("Block #{block_number}:");
        println!("  Hash: {block_hash}");
        println!("  Extrinsics:");

        // Log each of the extrinsic with it's associated events:
        let extrinsics = block.extrinsics().await?;
        for ext in extrinsics.iter() {
            let ext = ext?;
            let idx = ext.index();
            let events = ext.events().await?;
            let bytes_hex = format!("0x{}", hex::encode(ext.bytes()));

            // See the API docs for more ways to decode extrinsics:
            let decoded_ext = ext.as_root_extrinsic::<polkadot::Call>();

            println!("    Extrinsic #{idx}:");
            println!("      Bytes: {bytes_hex}");
            println!("      Decoded: {decoded_ext:?}");

            println!("      Events:");
            for evt in events.iter() {
                let evt = evt?;
                let pallet_name = evt.pallet_name();
                let event_name = evt.variant_name();
                let event_values = evt.field_values()?;

                println!("        {pallet_name}_{event_name}");
                println!("          {}", event_values);
            }

            println!("      Signed Extensions:");
            if let Some(signed_extensions) = ext.signed_extensions() {
                for signed_extension in signed_extensions.iter() {
                    let signed_extension = signed_extension?;
                    let name = signed_extension.name();
                    let value = signed_extension.value()?.to_string();
                    println!("        {name}: {value}");
                }
            }
        }
    }

    Ok(())
}