how can i send a transaction to a solana program using flutter/dart

Question

I have a solana program to which I want to send parameters and also different accounts, however I have not found how to do it, in this case I am using this flutter/dart library.

Flutter Packages [https://pub.dev/packages/solana_web3][1]

An example of how to communicate with a solana program in this case with the memo could be like this:

 Future<void> sendDataToContract(String s) async {
    // Create a connection to the Solana devnet.
    final connection = web3.Connection(web3.Cluster.devnet);
    // Get the program id of the smart contract.
    const programId = 'MemoSq4gqABAXKb96qnH8TysNcWxMyWCqXgDLGmfcHr';
    // Create the smart contract public key.
    final publicKey = web3.PublicKey.fromBase58(programId);
    final transaction = web3.Transaction();
    transaction.add(web3.TransactionInstruction(
      keys: [
        web3.AccountMeta(
          solanaMainWallet.publicKey,
          isSigner: true,
          isWritable: true,
        ),
      ],
      programId: publicKey,
      data: const Utf8Encoder().convert(s),
    ));

    // Send the transaction.
    var restul = await connection
        .sendAndConfirmTransaction(transaction, signers: [solanaMainWallet]);
    debugPrint('Tx successful with hash: $restul');
  }
}

the above code works great, but now i need to communicate with a different solana program a custom one, with a custom function, let's say in javascript it would be something like this:

const tx = await program.methods.createNft(nftMetadata.id, nftMetadata.name, nftMetadata.symbol, nftMetadata.uri, nftMetadata.price, nftMetadata.cant)
    .accounts({ mint: nftMintPda, tokenAccount: tokenAccount, metadataProgram: TOKEN_METADATA_PROGRAM_ID, masterEditionAccount: masterEditionAccountPda, payer: provider.wallet.publicKey, systemProgram: anchor.web3.SystemProgram.programId, rent: anchor.web3.SYSVAR_RENT_PUBKEY, nftMetadata: nftMetadataPdaMPL })
    .rpc()
    .catch(err => console.log(err));

in javascript to be able to access the method of the program we use "program.methods.createNft" but I don't know how to do this for flutter/dart.

final nftTransaction = web3.Transaction();
nftTransaction.add(web3.TransactionInstruction(
      keys: [
        web3.AccountMeta(
          nftMintPda.publicKey,
          isSigner: false,
          isWritable: true,
        ), //Mint account
        web3.AccountMeta(
          tokenAccount.publicKey,
          isSigner: false,
          isWritable: true,
        ),...
      ],
      programId: programIdPublicKey,
      data: args,
    ));
   
    // Send the transaction.
    var nftTxRestul = await connection.sendAndConfirmTransaction(nftTransaction, signers: [solanaMainWallet]);

If I send the transaction without specifying which method is going to be used, it returns the error:

101 (0x65) InstructionFallbackNotFound Fallback functions are not supported

Answer 1

Disclaimer, I don't have Flutter experience and I'm not familiar with the flutter library you linked, but I looked through their GH repo and see that they provide an implementation of the metaplex_token_metadata program..

I think you'll have to construct a Transaction like here, but instead of using SystemProgram you should use the MetaplexTokenMetadataProgram and TokenProgram to generate the instructions you want.

Roughly:

1. Create a Mint Account with intializeAccount and initializeMint
2. Create the token metadata with createMetadataAccountV3

hopefully that helps!