feat: Instantiate an event builder without a contract instance (#1882)

* Build an `Event` without requiring a contract instance

* Contract unit test

* Function to set Event address

* Example

* Typo to improve readability

* CHANGELOG

* cargo +nightly fmt

* FIX conflict

* review: applied Address alias

Co-authored-by: Andrea Simeoni <>
Co-authored-by: Georgios Konstantopoulos <me@gakonst.com>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Unreleased
 
+-   An `Event` builder can be instantiated specifying the event filter type, without the need to instantiate a contract.
 -   Add 'ethers_core::types::OpCode' and use in 'ethers_core::types::VMOperation' [1857](https://github.com/gakonst/ethers-rs/issues/1857)
 -   Remove rust_decimals dependency for ethers-core
 -   Add support for numbers greater than 2^96 for `ethers_core::utils::parse_units` [#1822](https://github.com/gakonst/ethers-rs/issues/1822)

ethers-contract/src/contract.rs

@@ -191,6 +191,19 @@ impl<M> Contract<M> {
     }
 }
 
+impl<M: Middleware> Contract<M> {
+    /// Returns an [`Event`](crate::builders::Event) builder for the provided event.
+    /// This function operates in a static context, then it does not require a `self`
+    /// to reference to instantiate an [`Event`](crate::builders::Event) builder.
+    pub fn event_of_type<'a, D: EthEvent>(client: &'a Arc<M>) -> Event<'a, M, D> {
+        Event {
+            provider: client,
+            filter: Filter::new().event(&D::abi_signature()),
+            datatype: PhantomData,
+        }
+    }
+}
+
 impl<M: Middleware> Contract<M> {
     /// Creates a new contract from the provided client, abi and address
     pub fn new(

ethers-contract/src/event.rs

@@ -2,8 +2,8 @@
 
 use crate::{log::LogMeta, stream::EventStream, ContractError, EthLogDecode};
 use ethers_core::{
-    abi::{Detokenize, RawLog},
+    abi::{Address, Detokenize, RawLog},
-    types::{BlockNumber, Filter, Log, Topic, H256},
+    types::{BlockNumber, Filter, Log, Topic, ValueOrArray, H256},
 };
 use ethers_providers::{FilterWatcher, Middleware, PubsubClient, SubscriptionStream};
 use std::{borrow::Cow, marker::PhantomData};
@@ -108,6 +108,12 @@ impl<M, D: EthLogDecode> Event<'_, M, D> {
         self.filter.topics[3] = Some(topic.into());
         self
     }
+
+    /// Sets the filter's address.
+    pub fn address(mut self, address: ValueOrArray<Address>) -> Self {
+        self.filter = self.filter.address(address);
+        self
+    }
 }
 
 impl<'a, M, D> Event<'a, M, D>

ethers-contract/tests/it/contract.rs

@@ -6,7 +6,7 @@ use ethers_core::types::{Filter, ValueOrArray, H256};
 #[cfg(not(feature = "celo"))]
 mod eth_tests {
     use super::*;
-    use ethers_contract::{LogMeta, Multicall, MulticallVersion};
+    use ethers_contract::{EthEvent, LogMeta, Multicall, MulticallVersion};
     use ethers_core::{
         abi::{encode, Detokenize, Token, Tokenizable},
         types::{transaction::eip712::Eip712, Address, BlockId, Bytes, I256, U256},
@@ -324,6 +324,21 @@ mod eth_tests {
         assert_eq!(log_2.address, contract_2.address());
     }
 
+    #[tokio::test]
+    async fn build_event_of_type() {
+        abigen!(
+            AggregatorInterface,
+            r#"[
+                event AnswerUpdated(int256 indexed current, uint256 indexed roundId, uint256 updatedAt)
+            ]"#,
+        );
+
+        let anvil = Anvil::new().spawn();
+        let client = connect(&anvil, 0);
+        let event = ethers_contract::Contract::event_of_type::<AnswerUpdatedFilter>(&client);
+        assert_eq!(event.filter, Filter::new().event(&AnswerUpdatedFilter::abi_signature()));
+    }
+
     #[tokio::test]
     async fn signer_on_node() {
         let (abi, bytecode) = compile_contract("SimpleStorage", "SimpleStorage.sol");

examples/subscribe_events_by_type.rs

@@ -0,0 +1,52 @@
+use ethers::{contract::Contract, prelude::*};
+use std::{error::Error, sync::Arc};
+abigen!(
+    AggregatorInterface,
+    r#"[
+        event AnswerUpdated(int256 indexed current, uint256 indexed roundId, uint256 updatedAt)
+    ]"#,
+);
+
+const PRICE_FEED_1: &str = "0x7de93682b9b5d80d45cd371f7a14f74d49b0914c";
+const PRICE_FEED_2: &str = "0x0f00392fcb466c0e4e4310d81b941e07b4d5a079";
+const PRICE_FEED_3: &str = "0xebf67ab8cff336d3f609127e8bbf8bd6dd93cd81";
+
+/// Subscribe to a typed event stream without requiring a `Contract` instance.
+/// In this example we subscribe Chainlink price feeds and filter out them
+/// by address.
+/// -------------------------------------------------------------------------------
+/// In order to run this example you need to include Ws and TLS features
+/// Run this example with
+/// `cargo run -p ethers --example subscribe_events_by_type --features="ws","rustls"`
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    let client = get_client().await;
+    let client = Arc::new(client);
+
+    // Build an Event by type. We are not tied to a contract instance. We use builder functions to
+    // refine the event filter
+    let event = Contract::event_of_type::<AnswerUpdatedFilter>(&client)
+        .from_block(16022082)
+        .to_block(16022282)
+        .address(ValueOrArray::Array(vec![
+            PRICE_FEED_1.parse()?,
+            PRICE_FEED_2.parse()?,
+            PRICE_FEED_3.parse()?,
+        ]));
+
+    let mut stream = event.subscribe_with_meta().await?;
+
+    // Note that `log` has type AnswerUpdatedFilter
+    while let Some(Ok((log, meta))) = stream.next().await {
+        println!("{:?}", log);
+        println!("{:?}", meta)
+    }
+
+    Ok(())
+}
+
+async fn get_client() -> Provider<Ws> {
+    Provider::<Ws>::connect("wss://mainnet.infura.io/ws/v3/c60b0bb42f8a4c6481ecd229eddaca27")
+        .await
+        .unwrap()
+}