Decoding Transactions

TransactionDecoder turns a Transaction's data field into a typed DecodedTransaction so you can pattern-match on the result instead of re-parsing hex-delimited strings.

It is a pure, stateless, zero-I/O decoder — no network round-trip, no ABI lookup. For full typed return decoding of contract calls, combine it with SmartContractController.

Example

import 'package:abidock_mvx/abidock_mvx.dart';

final decoded = const TransactionDecoder().decode(tx);

switch (decoded) {
  case NativeEgldTransfer(:final memo):
    print('EGLD memo: ${memo ?? '(none)'}');

  case EsdtTransfer(:final tokenIdentifier, :final amount, :final functionCall):
    print('$amount of $tokenIdentifier'
        '${functionCall == null ? '' : ' → ${functionCall.function}'}');

  case NftTransfer(:final collection, :final nonce, :final destination):
    print('$collection #$nonce → ${destination.bech32}');

  case MultiTransfer(:final transfers):
    print('${transfers.length} tokens bundled');

  case ContractCall(:final call):
    print('call ${call.function}(${call.arguments.length} args)');

  case ContractDeploy(:final bytecode, :final arguments):
    print('deploy ${bytecode.length} bytes of code, ${arguments.length} ctor args');

  case ContractUpgrade(:final bytecode):
    print('upgrade with ${bytecode.length} bytes');

  case ContractChangeOwner(:final newOwner):
    print('change owner → ${newOwner.bech32}');

  case ClaimDeveloperRewards():
    print('claim developer rewards');

  case UnknownTransaction(:final reason):
    print('could not decode: $reason');
}

Shapes recognised

Outcome	Input shape
NativeEgldTransfer	empty data, or free-form UTF-8 with no @ separators
EsdtTransfer	ESDTTransfer@<tokenHex>@<amountHex>[@<function>@<arg>...]
NftTransfer	ESDTNFTTransfer@<collectionHex>@<nonceHex>@<amountHex>@<destinationHex>[@<function>@<arg>...]
MultiTransfer	MultiESDTNFTTransfer@<destHex>@<countHex>@(<tokenHex>@<nonceHex>@<amountHex>)+[@<function>@<arg>...]
ContractCall	any other <function>@<argHex>... payload
ContractDeploy	<codeHex>@<vmTypeHex>@<metadataHex>[@<argHex>...] with receiver == Address.zero()
ContractUpgrade	upgradeContract@<codeHex>@<metadataHex>[@<argHex>...]
ContractChangeOwner	ChangeOwnerAddress@<newOwnerHex>
ClaimDeveloperRewards	ClaimDeveloperRewards (no args)
UnknownTransaction	invalid UTF-8, truncated transfer list, or malformed argument

The decoder never throws — anything it doesn't understand becomes UnknownTransaction with a reason string explaining what failed.

Inner contract calls

Token transfers frequently nest a contract call inside the data field (e.g. "send X WEGLD to router and call swap"). The ESDT/NFT/Multi outcomes all carry an optional functionCall that decodes the inner call when present:

if (decoded case EsdtTransfer(:final functionCall?) ) {
  print('Inner call: ${functionCall.function}');
  for (final arg in functionCall.arguments) {
    print('  arg: 0x${arg.map((b) => b.toRadixString(16).padLeft(2, '0')).join()}');
  }
}