Is there any function to calculate minimum amount needed to perform ethereum transaction?

[DiwakarThapa]

Hello,
I wanted to know is there any function in web3swift to validate minimum amount required to make transaction ?

[TonioMacaronio]

Hi, @DiwakarThapa
Think you need estimateGas function. It estimates a minimal amount of gas required to run a transaction. To do it the Ethereum node tries to run it and counts how much gas it consumes for computations. Setting the transaction gas limit lower than the estimate will most likely result in a failing transaction.
Usage example

let web3 = Web3.InfuraMainnetWeb3()
let sendToAddress = EthereumAddress("recepient_address")
let keystore = try! EthereumKeystoreV3(password: "")
let keystoreManager = KeystoreManager([tempKeystore!])
web3.addKeystoreManager(keystoreManager)
let contract = web3.contract(Web3.Utils.coldWalletABI, at: sendToAddress, abiVersion: 2)
guard let writeTX = contract?.write("fallback") else {return} // you can use any other tx method
writeTX.transactionOptions.from = tempKeystore!.addresses?.first // its your address
writeTX.transactionOptions.value = BigUInt("1.0", .eth) // value in eth
let estimate = try writeTX.estimateGasPromise().wait()
print(estimate) // here you'll get gas estimation

Hope this will help you