add subxt example

Cargo.toml

@@ -20,4 +20,11 @@ subxt = { version = "0.33", optional = true }
 [dev-dependencies]
 jsonrpsee = { version = "0.20.3", features = ["server"] }
 anyhow = "1"
-tracing-subscriber = { version = "0.3.17", features = ["env-filter"] }
+tracing-subscriber = { version = "0.3.17", features = ["env-filter"] }
+subxt = "0.33"
+subxt-signer = "0.33"
+
+[[example]]
+name = "hello_subxt"
+path = "examples/hello_subxt.rs"
+required-features = ["subxt"]

examples/hello_subxt.rs

@@ -0,0 +1,48 @@
+use reconnecting_jsonrpsee_ws_client::Client;
+use subxt::backend::rpc::RpcClient;
+use subxt::{OnlineClient, PolkadotConfig};
+use subxt_signer::sr25519::dev;
+use tracing_subscriber::util::SubscriberInitExt;
+
+// Generate an interface that we can use from the node's metadata.
+#[subxt::subxt(runtime_metadata_path = "examples/metadata.scale")]
+pub mod runtime {}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let filter = tracing_subscriber::EnvFilter::from_default_env();
+    tracing_subscriber::fmt()
+        .with_env_filter(filter)
+        .finish()
+        .init();
+
+    let rpc = Client::builder()
+        .build("ws://localhost:9944".to_string())
+        .await?;
+
+    // Create a new API client, configured to talk to Polkadot nodes.
+    let api: OnlineClient<PolkadotConfig> =
+        OnlineClient::from_rpc_client(RpcClient::new(rpc)).await?;
+
+    // Build a balance transfer extrinsic.
+    let dest = dev::bob().public_key().into();
+    let balance_transfer_tx = runtime::tx().balances().transfer_allow_death(dest, 10_000);
+
+    // Submit the balance transfer extrinsic from Alice, and wait for it to be successful
+    // and in a finalized block. We get back the extrinsic events if all is well.
+    let from = dev::alice();
+    let events = api
+        .tx()
+        .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
+        .await?
+        .wait_for_finalized_success()
+        .await?;
+
+    // Find a Transfer event and print it.
+    let transfer_event = events.find_first::<runtime::balances::events::Transfer>()?;
+    if let Some(event) = transfer_event {
+        println!("Balance transfer success: {event:?}");
+    }
+
+    Ok(())
+}