flutter web3dart how to get price from pancakeswap

Question

objective: try to get price from pancakeswap i created the abi and feed it with two contract addresss that i want the price from but i get this error| Unhandled Exception: type '_BigIntImpl' is not a subtype of type 'List' of 'data'

I think in the parameters i feed in the wrong TYPE when i call contract PS: i also try EthereumAddress as TYPE but does not work Your help is most appreciated

here is my code:

final pancakeSwapContract = '0x10ED43C718714eb63d5aA57B78B54704E256024E';
late Client httpClient;
late Web3Client ethereumClient;
late String _abiCode;
late Credentials _credentials;
String pancakeSwapConAddress = "0x10ED43C718714eb63d5aA57B78B54704E256024E";
String ethereumClientUrl = 'https://bsc-dataseed1.binance.org';
final bnbTokenAddress = "0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c";
final tokenAddres = '0xC75aa1Fa199EaC5adaBC832eA4522Cff6dFd521A';
@override
void initState() {
   super.initState();
   httpClient = Client();
   ethereumClient = Web3Client(ethereumClientUrl, httpClient);
}
Future<DeployedContract> getContract() async {
 String abi = await rootBundle.loadString("assets/abi/pancakeSwapAbi.json");
 String pancakeSwapConAddress ="0x10ED43C718714eb63d5aA57B78B54704E256024E".toLowerCase();
 DeployedContract contract = DeployedContract(
 ContractAbi.fromJson(abi, 'pancakeSwapAbi'),
 EthereumAddress.fromHex(pancakeSwapConAddress),
 );
return contract;
}

Future<void> calcBNBPrice() async {
 const bNBTokenAddress = "0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c"; //BNB
 const uSDTokenAddress = "0x55d398326f99059fF775485246999027B3197955"; //USDT
 // final EthereumAddress add1 = EthereumAddress.fromHex(bNBTokenAddress);
 // final EthereumAddress add2 = EthereumAddress.fromHex(uSDTokenAddress);
 DeployedContract contract = await getContract();
 getThePriceContract = contract.function("getAmountsOut");
 List<dynamic> gettingThePrice = await ethereumClient.call(
 contract: contract,
 function: getThePriceContract,
 params: [
  BigInt.parse(bNBTokenAddress),
  BigInt.parse(uSDTokenAddress),
 ],
);
final List<dynamic> convertResponse = gettingThePrice.first as List<dynamic>;
print(convertResponse);
}

ABI

[
    {
      "inputs": [
        {"internalType": "uint256", "name": "amountIn", "type": "uint256"},
        {"internalType": "address[]", "name": "path", "type": "address[]"}
      ],
      "name": "getAmountsOut",
      "outputs": [
        {"internalType": "uint256[]", "name": "amounts", "type": "uint256[]"}
      ],
      "stateMutability": "view",
      "type": "function"
    },
  ];

Kirill Vikhlyaev · Answer 1 · 2023-01-23T12:33:16.413

In ABI-file we have two types: uint256 - is BigInt in Flutter; address[] - array of EthereumAddresses.

   "inputs": [
            {
                "internalType": "uint256",
                "name": "amountIn",
                "type": "uint256" <--
            },
            {
                "internalType": "address[]",
                "name": "path",
                "type": "address[]" <--
            }
        ]

So, in arguments we need to write something like this:

params: <dynamic>[
    BigInt.from(1),
    [EthereumAddress.fromHex(tokens[0].address), EthereumAddress.fromHex(tokens[1].address)],
  ],

flutter web3dart how to get price from pancakeswap

1 Answers1