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Portal provides the function portal.api.simulateTransaction, which gives you insights into what will happen upon executing the transaction. Here’s how it works:
  • 5.x.x
  • 3.x.x
suspend fun simulateTransaction(): Result<String> {
    val evaluateTransactionParam = EvaluateTransactionParam(
      to = "0x5596D66388555273eF90163f5e7314C8CE14F73c", // The recipient address.
      value = "0x10DE4A2A", // The value to be sent in Wei.
      data = null, // Data for the transaction (for contract interactions).
      maxFeePerGas = null, // Maximum fee per gas.
      maxPriorityFeePerGas = null, // Maximum priority fee per gas.
      gas = null, // The gas limit.
      gasPrice = null, // Gas price in Wei.
    )

      val result = portal.api.evaluateTransaction(
        chainId = ETH_SEPOLIA_CHAIN_ID,
        operationType = EvaluateTransactionOperationType.SIMULATION,
        transaction = evaluateTransactionParam
      )

      if (result.isFailure) {
        return Result.failure(Exception("error: ${result.exceptionOrNull()?.message}"))
      }

    return Result.success("")
  }
This function will return the results of the transaction simulation:
  • changes: An array detailing all the potential transaction outcomes. Each change has the following structure:
    • amount: The amount being transferred.
    • assetType: The type of asset being dealt with (NATIVE or ERC20 or ERC721 or ERC1155 or SPECIAL_NFT).
    • changeType: The type of change (APPROVE or TRANSFER).
    • contractAddress: Address of the contract being interacted with (null for native transactions).
    • decimals: Decimals used in the asset.
    • from: The sender address.
    • name: The name of the asset.
    • rawAmount: The unformatted amount being transferred.
    • symbol: The asset’s symbol.
    • to: The receiver’s address.
    • tokenId: An identifier for tokens (null for assets that are not tokens).
  • gasUsed: The gas used by the transaction.
  • error: An object that contains the error message if the transaction would fail upon execution.
  • requestError: An object that contains the error message if there was an issue with the request, such as a malformed transaction argument being provided.
By incorporating transaction simulations, you can provide your users with a preview of the transaction outcomes and preemptively detect and handle errors, ensuring a smoother user experience. And now you are simulating transactions with Portal! 🙌 🚀 Next, we’ll explore how to back up the wallet for recovery if the user loses device access.
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