pezkuwi-subxt/examples/examples/fetch_constants.rs

// Copyright 2019-2022 Parity Technologies (UK) Ltd.
// This file is dual-licensed as Apache-2.0 or GPL-3.0.
// see LICENSE for license details.

//! To run this example, a local polkadot node should be running. Example verified against polkadot v0.9.28-9ffe6e9e3da.
//!
//! E.g.
//! ```bash
//! curl "https://github.com/paritytech/polkadot/releases/download/v0.9.28/polkadot" --output /usr/local/bin/polkadot --location
//! polkadot --dev --tmp
//! ```

use subxt::{
    OnlineClient,
    PolkadotConfig,
};

// Generate the API from a static metadata path.
#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata.scale")]
pub mod polkadot {}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    tracing_subscriber::fmt::init();

    // Create a client to use:
    let api = OnlineClient::<PolkadotConfig>::new().await?;

    // Build a constant address to query:
    let address = polkadot::constants().balances().existential_deposit();

    // Look it up:
    let existential_deposit = api.constants().at(&address)?;

    println!("Existential Deposit: {existential_deposit}");

    Ok(())
}