Guides

Listen to balances

Knowing the balance of a wallet is a fundamental operation in any blockchain application. You can query the balance of each wallet on-demand, but it is more efficient to listen to balance changes in real-time.

The example below shows how to retrieve and subscribe to balance updates.

Get balance using generated code


Future<void> main(List<String> arguments) async {
  final provider = Provider.fromUri(Uri.parse('wss://rpc.polkadot.io'));
  final polkadot = Polkadot(provider);

  // Account from SS58 address
  final account = Address.decode('19t9Q2ay58hMDaeg6eeBhqmHsRnc2jDMV3cYYw9zbc59HLj');

  // Retrieve Account Balance
  final accountInfo = await polkadot.query.system.account(account.pubkey);
  print('Balance: ${accountInfo.data.free}');

  // Output: Balance: 20109379543332
}

Listen to balance changes


Future<void> main(List<String arguments) async {
  final provider = Provider.fromUri(Uri.parse('wss://rpc.polkadot.io'));
  final polkadot = Polkadot(provider);

  final account = Address.decode('5HHJX1Nq3f6QH8HGxnCemyBQ4eAcpUwmKoLMw5AvboavPfrh');
  final storageKey = polkadot.query.system.accountKey(account.pubkey);

  polkadot.rpc.state.subscribeStorage([storageKey], (storage) {
    final accountInfo = AccountInfo.decode(Input.fromBytes(storage.changes[0].value!));
    print('Account Info: ${accountInfo.toJson()}');
  });

    // Output: Account Info: {nonce: 28, consumers: 1, providers: 1, sufficients: 0, data: {free: 1010064392159, reserved: 50611660000000, frozen: 0, flags: 170141183460469231731687303715884105728}}

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Interacting with ink! Smart Contracts

This guide demonstrates how to interact with ink! smart contracts using Polkadart. In this example, we use the Flipper contract to walk through the entire process—from setting up your environment to deploying and interacting with your contract.

Listen to new blocks

Blocks are the fundamental unit of time in a blockchain. They are created by the network every few seconds and contain a list of transactions that have been validated by the network.