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.
Many applications need to listen to new blocks as they are created in order to update their state or trigger some action. In the following snippet we are showing you how to listen to new blocks using Polkadart.
Future<void> main(List<String> arguments) async {
final provider = Provider.fromUri(Uri.parse('wss://rpc.polkadot.io'));
final subscription = await provider.subscribe('chain_subscribeNewHeads', []);
subscription.stream.forEach((response) {
print('New head: ${response.result}');
});
}
New head: {parentHash: 0x3754eb0ce660717868bf38b795075fcfc6aa203adb0929155f8cda241f5434b3, number: 0x1622278, stateRoot: 0x23f76264620c5c018dad925bcce8d881eea8e0388dd50c2f9214bcc1dc550ea3, extrinsicsRoot: 0x56e3a2a8642b6f651953eb57893c8fbf2e5500cf8a568a310f325cb9a52e9639, digest: {logs: [0x0642414245b501039f010000109b301100000000ee1dd8472584ffa6f214c229215366b3ad0e29cb71529e9835ac63114ac05877e44938bdfa3bb2b913364980d40db0523187406a3b05b534a5f1ef04516f960ea3625d9ae35b952e97df444965bd65ee569d0454a99aceca6dc5bac25091470a, 0x0442454546840335617d959f20181a3f85b44ab8055c51d5d2c5a0cfd5317466ab4fcd682903ad, 0x05424142450101423b8e5baa2963090161fc01eab9abf90eba3766aeb440bde6c1b01d8bc42f5301ec9e96d881fc7e683c596bfdfe0ccba427e7d22052818f401fa3f736559586]}}
New head: {parentHash: 0x230fdd23a0b5167bca1ca76a49187ac2d6af502d5106952b51f43513d3c7e15c, number: 0x1622279, stateRoot: 0x2402f9ed5aac51091ce35bb637ce0cdde8b5c619605f595378cc8817451d30ad, extrinsicsRoot: 0xb276911ad92e1882e49e8c54754127f5097ab0647fdc103ae80ac6a937375bb1, digest: {logs: [0x0642414245b5010318000000119b301100000000aa58edbb34b52bcd3875c2ec4a4191f5cf54b4ac9e9eece6fe503a259a9172459a99c1bba25454b6ed0135c1813480280e2f5d0fd13317128f694fd079d84b015252bfb306f52d38b631aa8c306396195a3d52fc5adb92b99956256fcda10c0a, 0x04424545468403befc57c5c4d15a74507a0f5baf3e28fd7a264981db1779604d896ea8eb991b85, 0x05424142450101c09e18c1c5cf39abf1b47523c53d03b798fa1a9f0e0d7e76c306af5e9c06fe3d399d869f970209b17cdd9155a51056169e3e1ba394b2a23514a17607d301fc8b]}}
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.
Make a balance transfer
Perhaps the most common operation done in any blockchain is transferring funds from one account to another. Here we will show you how to make a simple balance transfer using Polkadart.