pezkuwi-subxt/examples/examples/subscribe_all_events.rs

// Copyright 2019-2022 Parity Technologies (UK) Ltd.
// This file is part of subxt.
//
// subxt is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// subxt is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with subxt.  If not, see <http://www.gnu.org/licenses/>.

//! To run this example, a local polkadot node should be running. Example verified against polkadot 0.9.18-f6d6ab005d-aarch64-macos.
//!
//! E.g.
//! ```bash
//! curl "https://github.com/paritytech/polkadot/releases/download/v0.9.13/polkadot" --output /usr/local/bin/polkadot --location
//! polkadot --dev --tmp
//! ```

use futures::StreamExt;
use sp_keyring::AccountKeyring;
use std::time::Duration;
use subxt::{
    ClientBuilder,
    DefaultConfig,
    PairSigner,
    PolkadotExtrinsicParams,
};

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

/// Subscribe to all events, and then manually look through them and
/// pluck out the events that we care about.
#[async_std::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    env_logger::init();

    let api = ClientBuilder::new()
        .build()
        .await?
        .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, PolkadotExtrinsicParams<DefaultConfig>>>();

    // Subscribe to any events that occur:
    let mut event_sub = api.events().subscribe().await?;

    // While this subscription is active, balance transfers are made somewhere:
    async_std::task::spawn(async {
        let signer = PairSigner::new(AccountKeyring::Alice.pair());
        let api =
            ClientBuilder::new()
                .build()
                .await
                .unwrap()
                .to_runtime_api::<polkadot::RuntimeApi<
                    DefaultConfig,
                    PolkadotExtrinsicParams<DefaultConfig>,
                >>();

        let mut transfer_amount = 1_000_000_000;

        // Make small balance transfers from Alice to Bob in a loop:
        loop {
            api.tx()
                .balances()
                .transfer(AccountKeyring::Bob.to_account_id().into(), transfer_amount)
                .sign_and_submit_default(&signer)
                .await
                .unwrap();

            async_std::task::sleep(Duration::from_secs(10)).await;
            transfer_amount += 100_000_000;
        }
    });

    // Our subscription will see the events emitted as a result of this:
    while let Some(events) = event_sub.next().await {
        let events = events?;
        let block_hash = events.block_hash();

        // We can iterate, statically decoding all events if we want:
        println!("All events in block {block_hash:?}:");
        println!("  Static event details:");
        for event in events.iter() {
            let event = event?;
            println!("    {event:?}");
        }

        // Or we can dynamically decode events:
        println!("  Dynamic event details: {block_hash:?}:");
        for event in events.iter_raw() {
            let event = event?;
            let is_balance_transfer = event
                .as_event::<polkadot::balances::events::Transfer>()?
                .is_some();
            let pallet = event.pallet;
            let variant = event.variant;
            println!(
                "    {pallet}::{variant} (is balance transfer? {is_balance_transfer})"
            );
        }

        // Or we can dynamically find the first transfer event, ignoring any others:
        let transfer_event =
            events.find_first::<polkadot::balances::events::Transfer>()?;

        if let Some(ev) = transfer_event {
            println!("  - Balance transfer success: value: {:?}", ev.amount);
        } else {
            println!("  - No balance transfer event found in this block");
        }
    }

    Ok(())
}