Here we will discuss how to use `ethers-rs` to subscribe and listen to blocks, events, and logs. Subscriptions provide a way to receive real-time updates on various activities on the Ethereum blockchain, allowing you to monitor the network and react to changes as they happen.
ethers-rs offers a convenient way to work with subscriptions, enabling you to listen to new blocks, transaction receipts, and logs. The main components you will work with are:
1. Provider: The main struct used to interact with the Ethereum network.
2. SubscriptionStream: A stream of updates you can subscribe to for real-time notifications.
## Getting Started
Before working with subscriptions, make sure you have ethers-rs added to your project's dependencies in Cargo.toml:
```toml
[dependencies]
ethers = { version = "2.0.0", features = ["full"] }
```
Next, import the necessary components from the ethers-rs library:
```rust
use ethers::{prelude::\*,types::H256,};
```
### Subscribing to Events
As we discussed in the previous section on events, you can subscribe to specific events emitted by smart contracts using the EventWatcher struct. To create a SubscriptionStream, call the subscribe method on your EventWatcher:
```rust
let mut stream = watcher.subscribe().await?;
```
Now, you can listen to events as they are emitted by the smart contract:
```rust
while let Some(event) = stream.next().await {
match event {
Ok(log) => {
println!("New event: {:?}", log);
}
Err(e) => {
eprintln!("Error: {:?}", e);
}
}
}
```
By using the subscription features provided by ethers-rs, you can efficiently monitor and react to various activities on the Ethereum network. Subscriptions are a powerful tool for building responsive and dynamic applications that can interact with smart contracts and stay up-to-date with the latest network events.
### Unsubscribing from Subscriptions
In some cases, you may want to stop listening to a subscription. To do this, simply drop the SubscriptionStream:
```rust
drop(stream);
```
This will stop the stream from receiving any further updates.
