Read storage

Reading the storage also called the chain state is a common operation in blockchain development. The storage can hold anything from balance of an account to the configuration of the chain. It is also possible to read the storage from a specific block, which is useful for historical data analysis.

Here we are showing you how to retrieve the storage and decode it.

Reading storage from the current block

import 'package:demo/generated/polkadot/polkadot.dart';
import 'package:polkadart/polkadart.dart';

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

  polkadot.query.system.number().then((blockNumber) {
    print('Current block number: $blockNumber');
  });
}

// Output: Current block number: 23208989

Reading storage from a specific block

import 'package:demo/generated/polkadot/polkadot.dart';
import 'package:polkadart/polkadart.dart';
import 'package:polkadart/scale_codec.dart';

Future<void> main(List<String> arguments) async {
  final provider = Provider.fromUri(Uri.parse('wss://rpc.polkadot.io'));
  final polkadot = Polkadot(provider);
  final block = decodeHex('0x43c65760a5e36e9c95b2c493b78e7b01a2f8be5b0b48d543168d9f2c6fc4eb10');

  polkadot.query.system.number(at: block).then((blockNumber) {
    print('Current block number: $blockNumber');
  });
}

// Output: Current block number: 23208972