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Portal provides the function portal.evaluateTransaction, which gives you insights into what will happen upon executing the transaction. This function can perform transaction simulation, security validation, or both. Here’s how it works: 
// Basic transaction evaluation
do {
    let transaction = EvaluateTransactionParam(
        to: "0x742d35Cc6634C0532925a3b844Bc454e4438f44e",
        value: "1000000000000000000", // 1 ETH
        data: nil,
        maxFeePerGas: "30000000000",
        maxPriorityFeePerGas: "1500000000",
        gas: "21000",
        gasPrice: nil
    )

    let evaluation = try await portal.evaluateTransaction(
        chainId: "eip155:1",
        transaction: transaction,
        operationType: .all
    )

    // Check validation results
    if let validation = evaluation.validation {
        print("Security Status: \(validation.status)")

        if validation.status != "VALIDATED" {
            print("Warning: \(validation.description ?? "Unknown issue")")

            // Print detected security features
            validation.features.forEach { feature in
                print("Security Feature: \(feature.type)")
                print("Description: \(feature.description)")
            }
        }
    }

    // Check simulation results
    if let simulation = evaluation.simulation {
        print("Simulation Status: \(simulation.status)")

        // Print asset changes
        simulation.assetsDiffs.forEach { (token, diffs) in
            print("\nToken: \(token)")
            diffs.forEach { diff in
                print("Incoming transfers:")
                diff.in.forEach { transfer in
                    print(transfer)
                }
                print("Outgoing transfers:")
                diff.out.forEach { transfer in
                    print(transfer)
                }
            }
        }
    }
} catch {
    print("Evaluation failed: \(error)")
}

// Contract interaction evaluation
do {
    let transaction = EvaluateTransactionParam(
        to: "0x742d35Cc6634C0532925a3b844Bc454e4438f44e",
        value: "0",
        data: "0xa9059cbb000000000000000000000000742d35cc6634c0532925a3b844bc454e4438f44e0000000000000000000000000000000000000000000000000de0b6b3a7640000", // ERC20 transfer
        maxFeePerGas: nil,
        maxPriorityFeePerGas: nil,
        gas: "65000",
        gasPrice: "20000000000"
    )

    // Validate only
    let validation = try await portal.evaluateTransaction(
        chainId: "eip155:1",
        transaction: transaction,
        operationType: .validation
    )

    if let validationResult = validation.validation {
        // Handle potential security issues
        switch validationResult.status {
        case "VALIDATED":
            print("Transaction is safe")
        case "WARNING":
            print("Warning: \(validationResult.description ?? "Unknown warning")")
        case "BLOCKED":
            print("Blocked: \(validationResult.reason ?? "Unknown reason")")
        default:
            print("Unknown status: \(validationResult.status)")
        }
    }
} catch {
    print("Validation failed: \(error)")
}
The operationType parameter determines what type of evaluation is performed. It can be one of the following values: 
public enum EvaluateTransactionOperationType: String, CaseIterable {
  case validation  // Perform security validation only
  case simulation  // Perform transaction simulation only
  case all         // Perform both validation and simulation
}
This function returns a BlockaidValidateTrxRes containing:
  • simulation: Transaction simulation results including:
    • accountAddress: Address being analyzed
    • accountSummary: Summary of account state changes
    • addressDetails: Detailed information about involved addresses
    • assetsDiffs: Asset balance changes, containing:
      • asset: Asset information
      • in: Incoming transfers
      • out: Outgoing transfers
    • exposures: Risk exposure analysis
    • status: Simulation status
    • totalUsdDiff: Total USD value change
    • totalUsdExposure: Total USD value at risk
  • validation: Security validation results (when operationType is .validation or .all) including:
    • classification: Type of potential security issue
    • description: Detailed description of the validation results
    • features: Array of detected security features
    • status: Validation status
  • block: Block number used for evaluation
  • chain: Chain identifier
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. Related Documentation