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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.

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.

Make a transfer


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

  final wallet = await KeyPair.sr25519.fromUri("//Alice");
  print('Alice\' wallet: ${wallet.address}');

  // Get information necessary to build a proper extrinsic
  final runtimeVersion = await polkadot.rpc.state.getRuntimeVersion();
  final currentBlockNumber = (await polkadot.query.system.number()) - 1;
  final currentBlockHash = await polkadot.query.system.blockHash(currentBlockNumber);
  final genesisHash = await polkadot.query.system.blockHash(0);
  final nonce = await polkadot.rpc.system.accountNextIndex(wallet.address);

  // Make the encoded call
  final multiAddress = $MultiAddress().id(wallet.publicKey.bytes);
  final transferCall = polkadot.tx.balances.transferKeepAlive(dest: multiAddress, value: BigInt.one);
  final encodedCall = transferCall.encode();

  // Make the payload
  final payload = SigningPayload(
      method: encodedCall,
      specVersion: runtimeVersion.specVersion,
      transactionVersion: runtimeVersion.transactionVersion,
      genesisHash: encodeHex(genesisHash),
      blockHash: encodeHex(currentBlockHash),
      blockNumber: currentBlockNumber,
      eraPeriod: 64,
      nonce: nonce,
      tip: 0).encode(polkadot.registry);

  // Sign the payload and build the final extrinsic
  final signature = wallet.sign(payload);
  final extrinsic = ExtrinsicPayload(
    signer: wallet.bytes(),
    method: encodedCall,
    signature: signature,
    eraPeriod: 64,
    blockNumber: currentBlockNumber,
    nonce: nonce,
    tip: 0,
  ).encode(polkadot.registry, SignatureType.sr25519);

  // Send the extrinsic to the blockchain
  final author = AuthorApi(provider);
  await author.submitAndWatchExtrinsic(extrinsic, (data) {
    print(data);
  });
}

// Output:
// Alice' wallet: 5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY
// ready: null
// broadcast: [12D3KooWH6tanw7GDdvspfEpt2gEbn82Na84deJDnMNJptJCfAKU, 12D3KooWN8pzDyuAAZ126uR6WcwYThbMWSPnXf7cimKHCZVn34iB, 12D3KooWDUjbGEP1fExf7LDze8iScY6ycsB8B7K3Gfnb2wwffhxK, 12D3KooWHTuZXi5jfAztC68Wf9wbHk8g3pFs9uUVpw9tib13zQWf, 12D3KooWGGBCu1AwCLt5LWE63RTPorR3PjX7Q3cDZrRku59NPkB5, 12D3KooWB6iwHFUoLpSxp6jNCkExzukVJF1hKWNRBvZWtt34gVXh, 12D3KooWEtK675m8iU8Hpc1E5SLnBMPZgzZfdp4uUGDmyh7LEgR3, 12D3KooW9zVuJRTqsPJ5KoA7QSPzCxesYT8FhAKRDwdLdYXAkim3, 12D3KooWPgHhBcG2zD6uND3M6XWdd8MuXCU2Z6xjZs5typTVqUVd, 12D3KooWGQudnpbyypxqUmQdsmpGCfHDu9ip4oqeMM4M4pPxcSmJ, 12D3KooWSS1FFy4VgJmf5kioR5MotCS3LFNHWM3Z1GxQfmUcKqiy, 12D3KooWQZkoqjez2aJ8GsTf1K5vCY2PV3XxwVf9B3iuuYYxViEE, 12D3KooWHHyDiQXNvgtW2pxNsgGntpz6AuSni3Dgem6EYY7PeMZM, 12D3KooWLJ5DEEcifVAXnJZAyznxd6xWsEvwS6U43nD5JmUxQGPb, 12D3KooWADSbUQbTLHf4dzp8NtWK3DJFj3TSyWxv3v1wooCU77YC, 12D3KooWCmUArt3vWrmNTCtvXf7RCWWhgSgU5jUcqD1cgPiL7w1z, 12D3KooWPe66mj1D4T4KcwsJikeJScxSVNS2iae6oJHGnF99DTLc, 12D3KooWH3toosYujUH3jvZDrVsudJp9CEUc8ajyNGAUeMvRYqYd, 12D3KooWAuKeacpNPdFq7sLjXmgS23SyGu4Us7Z4fRiJoVK3aky2, 12D3KooWFUUj8yJ3sJzXjtPZAvhuK1bAhbn9JPa7KAYCoDN1MLmZ, 12D3KooWCx3GoZeH2MZ4eFmqeYa9RPppC4eZopW8GbEgyYcrrhQA, 12D3KooWPWHUu17HfaPuK7fbszNd6chFDzwHL3HCVw5miNfAKjLN, 12D3KooWPWRX8XUxV3pYeYb1fZpK2RSycTFhrVZ4Su65HxuYzRSh, 12D3KooWH57Fx8xR8FJhkDuvZDg2Jav3ZEJohjMtyLC1CGXVZ1vK, 12D3KooWLc4ieE6EGZ3B8yZ7JnaQqJKU7ocGXRVNufkE9Nh8E3XQ, 12D3KooWCRcoJqxeKVDTcKxqv4kdeUGkoJkWggZJyhrfhh4jAHY4, 12D3KooWAwWmTPHPeUruUrAm53KjUrAGVqdwSKPmRa7RC65yE7aL, 12D3KooWRuAURXtSTkbiz6tccf6QhABKuYmQw2w3wy16ZjhAQEsA, 12D3KooWAgv6KKySREnXRy6V136VM7orMtLTdXifcLkofUTeN76o, 12D3KooWLnf7gQkZVjDcKkoxfxAYuoJZcFukkV3zvkNMvYwvZLV4, 12D3KooWDjsafUnHj8SfCuG8pYBzNFMbq8GuTWQ9AT1SbSa4X3qy, 12D3KooWQj2P4jDanJtktEJnTFqbtv8rqo8s3iqaTi58yE5GMoPa, 12D3KooWJhMu1NSHC2xJgSi73GznghPXBc6oq2VZdUYvJJd8MLU7, 12D3KooWSz85vPmCcQ9fwaHpSrPyaAXRP2fB5phetz6txD444Jmn, 12D3KooWKz8dMRwWnw7UVZrrWegYBPBufBhpxBYSjk4JELyxKrTS, 12D3KooWLcFJj4mvUBD38FckCqafTYavJxZBeQknxVAvkhMFATiB, 12D3KooWNgzmWzP2cdDoinwsCva1vrXdN1bKHbnrzvkz66hQhmtc, 12D3KooWAbPXnoRSng2B5W9rXwz2A3tVrPMy8brnSvmDcyvnJs7X, 12D3KooWRmVgYuBa54Xo225zBAhfesdSPM8TL5JruNmYFUa5m9dP, 12D3KooW9xysa5Q6KuANonoMBp8AgYpCAcpyUk6Z2wxpEbN4ru2N]
// inBlock: 0xc3c341788f41a28046b7e0cac16629a2205acf1259ebfb5b52da0f2ae9e09959
// finalized: 0xc3c341788f41a28046b7e0cac16629a2205acf1259ebfb5b52da0f2ae9e09959

Using ExtrinsicBuilder (Fluent API)

For a more streamlined experience, you can use the ExtrinsicBuilder which handles much of the boilerplate automatically:


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

  final wallet = await KeyPair.sr25519.fromUri("//Alice");
  print('Alice\' wallet: ${wallet.address}');

  // Create the transfer call
  final multiAddress = $MultiAddress().id(wallet.publicKey.bytes);
  final transferCall = polkadot.tx.balances.transferKeepAlive(dest: multiAddress, value: BigInt.one);

  // Build and sign the extrinsic using the fluent builder
  final extrinsic = await ExtrinsicBuilder(polkadot)
      .call(transferCall)
      .signer(wallet)
      .build();

  // Send the extrinsic
  final author = AuthorApi(provider);
  await author.submitAndWatchExtrinsic(extrinsic, (data) {
    print(data);
  });
}

The ExtrinsicBuilder automatically fetches runtime version, block hash, nonce, and other required information, making it easier to construct valid extrinsics.

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.

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.