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Filter one or multiple events by type from an EventSubscription (#461)
* Split events.rs into multiple files and start work on FilterEvents * First pass filtering event(s) * Tweak event examples to show filter_events * cargo clippy + fmt * consistify and tidy * cargo fmt * Tweak a couple of comments * Expose phase and block_hash of filtered events, too * cargo fmt * expose FilteredEventDetails * Add docs * cargo clippy * remove FilterEvents knowledge of EventSubscription so it's easier to unit test * unit test filter_events * tweak an integration test to use filter_events * cargo fmt * cargo clippy * Tweak a comment Co-authored-by: David <[email protected]> Co-authored-by: David <[email protected]>
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| // 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/>. | ||
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| //! To run this example, a local polkadot node should be running. Example verified against polkadot 0.9.13-82616422d0-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, | ||
| DefaultExtra, | ||
| PairSigner, | ||
| }; | ||
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| #[subxt::subxt(runtime_metadata_path = "examples/polkadot_metadata.scale")] | ||
| pub mod polkadot {} | ||
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| /// 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(); | ||
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| // Subscribe to any events that occur: | ||
| let api = ClientBuilder::new() | ||
| .build() | ||
| .await? | ||
| .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, DefaultExtra<DefaultConfig>>>(); | ||
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| // Subscribe to several balance related events. If we ask for more than one event, | ||
| // we'll be given a correpsonding tuple of `Option`'s, with exactly one | ||
| // variant populated each time. | ||
| let mut balance_events = api.events().subscribe().await?.filter_events::<( | ||
| polkadot::balances::events::Withdraw, | ||
| polkadot::balances::events::Transfer, | ||
| polkadot::balances::events::Deposit, | ||
| )>(); | ||
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| // While this subscription is active, we imagine some balance transfers are made somewhere else: | ||
| 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, DefaultExtra<DefaultConfig>>>(); | ||
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| // Make small balance transfers from Alice to Bob in a loop: | ||
| loop { | ||
| api.tx() | ||
| .balances() | ||
| .transfer(AccountKeyring::Bob.to_account_id().into(), 1_000_000_000) | ||
| .sign_and_submit(&signer) | ||
| .await | ||
| .unwrap(); | ||
| async_std::task::sleep(Duration::from_secs(10)).await; | ||
| } | ||
| }); | ||
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| // Our subscription will see all of the balance events we're filtering on: | ||
| while let Some(ev) = balance_events.next().await { | ||
| let event_details = ev?; | ||
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| let block_hash = event_details.block_hash; | ||
| let event = event_details.event; | ||
| println!("Event at {:?}:", block_hash); | ||
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| if let (Some(withdraw), _, _) = &event { | ||
| println!(" Withdraw event: {withdraw:?}"); | ||
| } | ||
| if let (_, Some(transfer), _) = &event { | ||
| println!(" Transfer event: {transfer:?}"); | ||
| } | ||
| if let (_, _, Some(deposit)) = &event { | ||
| println!(" Deposit event: {deposit:?}"); | ||
| } | ||
| } | ||
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| Ok(()) | ||
| } |
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