Swapping using Uniswap - ethereum

Here is my code:
// SPDX-License-Identifier: UNLICENCED
pragma solidity <0.9.0;
interface UniswapInterface{
function swapExactTokensForTokens(
uint amountIn,
uint amountOutMin,
address[] calldata path,
address to,
uint deadline
) external returns (uint[] memory amounts);
}
interface IERC20{
function balanceOf(address account) external view returns (uint256);
function decimals() external view returns (uint8);
function transfer(address recipient, uint256 amount) external returns (bool);
function allowance(address owner, address spender) external view returns (uint256);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
}
contract swapContract{
address public UniSwapRouterAddress = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;
address public USDCAddress = 0x2fB298BDbeF468638AD6653FF8376575ea41e768;
address public BTCAddress = 0x577D296678535e4903D59A4C929B718e1D575e0A;
IERC20 USDC = IERC20(0x2fB298BDbeF468638AD6653FF8376575ea41e768);
IERC20 BTC = IERC20(0x577D296678535e4903D59A4C929B718e1D575e0A);
UniswapInterface UniSwapRouter = UniswapInterface(UniSwapRouterAddress);
function approveUSDC() public{
USDC.approve(UniSwapRouterAddress, 999**9);
}
function approveBTC() public{
BTC.approve(UniSwapRouterAddress, 999**9);
}
function deposit(uint256 amount) public{
require(amount > 0, "0 is not accepted!");
uint256 allowance = USDC.allowance(msg.sender, address(this));
require(allowance >= amount, "Check USDC allowance");
USDC.transferFrom(msg.sender, address(this), amount);
}
function withdraw() public {
USDC.transfer(msg.sender, USDC.balanceOf(address(this)));
}
function swapUSDC() public {
address[] memory Path = new address[](2);
Path[0] = USDCAddress;
Path[1] = BTCAddress;
UniSwapRouter.swapExactTokensForTokens(
100000000,
0,
Path,
address(this),
block.timestamp + 240
);
}
}
I simply want to swap 1 USDC (its decimal is 8) to BTC on Rinkeby testnetwork.
I tried so many changes like increasing deadline, change in amountIn and amountOutMin but no gain. Also the pool on Uniswap has liquidity.
The error just says:
Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
execution reverted
I have checked the stackoverflow for answer but could not find a solution

I tried to figure out what the problem might be and realized that most likely there is no such pool.
If you go to the Uniswap UI, you will see that the pool was created only for V3, and you are trying to use the V2 address of router.
There are two ways to solve the problem, the first is to create a liquidity pool in V2 or to make an exchange through V3.

Related

Transaction is getting reverted in the `refundToInsurer()` function call

The deployment of InsuranceProvider is working fine and the calling of newContract() with the required parameters is successfully creating/deploying the InsuranceConsumer contract. Even, the payOutContract() is working correctly in terms of transferring the ETH balance from the InsuranceConsumer to the client's wallet.
The issue is with the refundToInsurer() function, as it's expected to transfer the ETH balance from the InsuranceConsumer to the insurer's wallet, but it's transaction is getting failed/reverted.
Here's the code:
SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
import "#chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
contract InsuranceProvider {
address payable public insurer;
AggregatorV3Interface internal priceFeed;
modifier onlyOwner() {
require(insurer == msg.sender, "Only Insurance provider can do this");
_;
}
constructor() payable {
priceFeed = AggregatorV3Interface(
0xD4a33860578De61DBAbDc8BFdb98FD742fA7028e
);
insurer = payable(msg.sender);
}
function newContract(
address payable _client,
uint256 _premium,
uint256 _payoutValue
) public payable onlyOwner returns (address) {
//create contract, send payout amount so contract is fully funded plus a small buffer
InsuranceConsumer i = (new InsuranceConsumer){
value: ((_payoutValue * 1 ether) / (uint256(getLatestPrice())))
}(_client, _premium, _payoutValue);
return address(i);
}
function getLatestPrice() public view returns (int256) {
(, int256 price, , uint256 timeStamp, ) = priceFeed.latestRoundData();
// If the round is not complete yet, timestamp is 0
require(timeStamp > 0, "Round not complete");
return price;
}
function payOutContract(address _contract) public {
InsuranceConsumer i = InsuranceConsumer(_contract);
// Transfer agreed amount to client
i.payOutContract();
}
function refundToInsurer(address _contract) public onlyOwner {
InsuranceConsumer i = InsuranceConsumer(_contract);
// Transfer back the amount to insurer
i.refundToInsurer();
}
}
contract InsuranceConsumer {
AggregatorV3Interface internal priceFeed;
address payable public insurer;
address payable client;
uint256 startDate;
uint256 premium;
uint256 payoutValue;
constructor(
address payable _client,
uint256 _premium,
uint256 _payoutValue
) payable {
//set ETH/USD Price Feed
priceFeed = AggregatorV3Interface(
0xD4a33860578De61DBAbDc8BFdb98FD742fA7028e
);
//first ensure insurer has fully funded the contract
require(
msg.value >= _payoutValue / uint256(getLatestPrice()),
"Not enough funds sent to contract"
);
//now initialize values for the contract
insurer = payable(msg.sender);
client = _client;
startDate = block.timestamp; //contract will be effective immediately on creation
premium = _premium;
payoutValue = _payoutValue;
}
function payOutContract() public {
//Transfer agreed amount to client
client.transfer(address(this).balance);
}
function refundToInsurer() public {
// Transfer back the amount to insurer
insurer.transfer(address(this).balance);
}
function getLatestPrice() public view returns (int256) {
(, int256 price, , uint256 timeStamp, ) = priceFeed.latestRoundData();
// If the round is not complete yet, timestamp is 0
require(timeStamp > 0, "Round not complete");
return price;
}
}
Can anyone please help by pointing out the logical mistake that I'm doing in the refundToInsurer() function ?
As, we're creating the InsuranceConsumer using the newContract() function of InsuranceProvider. Therefore, the msg.sender of the InsuranceConsumer is going to be the InsuranceProvider itself, not the insurer's wallet.
So, when we're calling the refundInsurer() of InsuranceConsumer via InsuranceProvider, then it's doing:
insurer.transfer(address(this).balance);
It means to transfer the available ETH in the InsuranceConsumer to the InsuranceProvider (not the insurer's wallet), and since InsuranceProvider is not expected to be a receiver, that's why it's reverting the transaction.
So, the corrected code will be:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
import "#chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
contract InsuranceProvider {
address payable public insurer;
AggregatorV3Interface internal priceFeed;
modifier onlyOwner() {
require(insurer == msg.sender, "Only Insurance provider can do this");
_;
}
constructor() payable {
priceFeed = AggregatorV3Interface(
0xD4a33860578De61DBAbDc8BFdb98FD742fA7028e
);
insurer = payable(msg.sender);
}
function newContract(
address payable _client,
uint256 _premium,
uint256 _payoutValue
) public payable onlyOwner returns (address) {
//create contract, send payout amount so contract is fully funded plus a small buffer
InsuranceConsumer i = (new InsuranceConsumer){
value: ((_payoutValue * 1 ether) / (uint256(getLatestPrice())))
}(_client, _premium, _payoutValue);
return address(i);
}
function getLatestPrice() public view returns (int256) {
(, int256 price, , uint256 timeStamp, ) = priceFeed.latestRoundData();
// If the round is not complete yet, timestamp is 0
require(timeStamp > 0, "Round not complete");
return price;
}
function payOutContract(address _contract) public onlyOwner {
// Transfer agreed amount to client
InsuranceConsumer i = InsuranceConsumer(_contract);
i.payOutContract();
}
function refundToInsurer(address _contract) public onlyOwner {
// Transfer back the amount to insurer
InsuranceConsumer i = InsuranceConsumer(_contract);
i.refundToInsurer(insurer);
}
}
contract InsuranceConsumer {
AggregatorV3Interface internal priceFeed;
address payable public insurer;
address payable client;
uint256 startDate;
uint256 premium;
uint256 payoutValue;
constructor(
address payable _client,
uint256 _premium,
uint256 _payoutValue
) payable {
//set ETH/USD Price Feed
priceFeed = AggregatorV3Interface(
0xD4a33860578De61DBAbDc8BFdb98FD742fA7028e
);
//first ensure insurer has fully funded the contract
require(
msg.value >= _payoutValue / uint256(getLatestPrice()),
"Not enough funds sent to contract"
);
//now initialize values for the contract
insurer = payable(msg.sender);
client = _client;
startDate = block.timestamp; //contract will be effective immediately on creation
premium = _premium;
payoutValue = _payoutValue;
}
function payOutContract() public {
//Transfer agreed amount to client
client.transfer(address(this).balance);
}
function refundToInsurer(address payable _insurer) public {
// Transfer back the amount to insurer
_insurer.transfer(address(this).balance);
}
function getLatestPrice() public view returns (int256) {
(, int256 price, , uint256 timeStamp, ) = priceFeed.latestRoundData();
// If the round is not complete yet, timestamp is 0
require(timeStamp > 0, "Round not complete");
return price;
}
}
Now, while calling the refundInsurer(), we're explicitly passing the insurer as the parameter, and it's taking the value of msg.sender from InsuranceProvider, so the msg.sender is going to be the insurer's wallet (with which the InsuranceProvider is being deployed) in this case.
And now, when we're calling the refundInsurer() of InsuranceConsumer via InsuranceProvider, then it's doing:
_insurer.transfer(address(this).balance);
It means to transfer the available ETH in the InsuranceConsumer to the insurer's wallet. So, the transaction will be successful resulting in the withdrawal of the funds from the InsuranceConsumer to the insurer's wallet.

How to fix 'TransferHelper: ETH_TRANSFER_FAILED' when interacting with Uni V2

I'm dealing with a strange issue with the safeTransferETH helper function in Uniswap V2's router contract.
I'm trying to swap tokens held by the contract to Uniswap for Ether, using the swapExactTokensForETH function provided by the Uniswap V2 router. (The function code is present on Uniswap's github in router1). The function being called is:
function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
external
override
ensure(deadline)
returns (uint[] memory amounts)
{
require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
TransferHelper.safeTransferFrom(path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]);
_swap(amounts, path, address(this));
IWETH(WETH).withdraw(amounts[amounts.length - 1]);
TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
}
The only part of this code that is throwing an error is the TransferHelper.safeTransferETH function, which is:
function safeTransferETH(address to, uint value) internal {
(bool success,) = to.call{value:value}(new bytes(0));
require(success, 'TransferHelper: ETH_TRANSFER_FAILED');
}
My code is:
function uniV2ReceiveETH(address _token0, uint _amount0) public payable returns (uint[] memory amountsReceived) {
require(_amount0 > 0, "Must provide tokens if we want tokens in return!");
address[] memory path = new address[](2);
path[0] = _token0;
path[1] = WETH;
IERC20 token;
token = IERC20(_token0);
if (token.balanceOf(address(this)) > 0) {
_amount0 = token.balanceOf(address(this));
}
require(token.approve(address(uniV2Router), _amount0 + 10000), "approval failed");
// Swap logic
uint amountOutMin = UniswapV2Library.getAmountsOut(address(uniV2Factory), _amount0, path)[1];
amountsReceived = uniV2Router.swapExactTokensForETH(_amount0, amountOutMin, path, address(this), deadline);
uint endBalance = address(this).balance;
// Let everyone know we're done!
emit Swap(msg.sender, _amount0, endBalance);
}
A few other notes are:
The contract does receive ETH from other addresses without issue.
I am using hardhat, and a forked version of the mainnet to test.
The contract also works with the Uniswap router's other swap functions, including SwapExactETHForTokens and SwapExactTokensForTokens.
I solved this issue by having a payable fallback function by defining it as:
fallback() external payable { }
inside my smart contract.
Add to your contract.
receive() external payable {}
fallback() external payable {}

Attn: call to FundMe.getVersion errored: VM execution error. Reverted 0x

How do I fix this issue?
The 0x5f4e... address hardcoded in your getVersion() function doesn't hold any smart contract on the Kovan testnet (link). Even though it has a contract deployed on the mainnet, these environments are separated.
When there's no smart contract on the address, there's nothing to send a response to the internal call. Your code expects an uint256 response from the version() call, so that it can return it from the getVersion().
When it doesn't receive the expected response, it throws an exception, effectively reverting the "main" call.
/ SPDX-License-Identifier: MIT
pragma solidity >=0.6.6 <0.9.0;
interface AggregatorV3Interface {
function decimals()
external view returns (
uint8
);
function description()
external view returns (
string memory
);
function version()
external view returns (
uint256
);
// getRoundData and latestRoundData should both raise "No data present"
// if they do not have data to report, instead of returning unset values
// which could be misinterpreted as actual reported values.
function getRoundData(
uint80 _roundId
)
external view returns (
uint80 roundId,
int256 answer,
uint256 startedAt,
uint256 updatedAt,
uint80 answeredInRound
);
function latestRoundData()
external view returns (
uint80 roundId,
int256 answer,
uint256 startedAt,
uint256 updatedAt,
uint80 answeredInRound
);
}
contract FundMe {
mapping(address =>uint256) public addressToAmountFunded;
function fund() public payable {
addressToAmountFunded[msg.sender] += msg.value;
//What the eth --> usd conversion rate
}
function getVersion() public view returns (uint256) {
AggregatorV3Interface priceFeed = AggregatorV3Interface(0x8A753747A1Fa494EC906cE90E9f37563A8AF630e);
return priceFeed.version();
}
}
AggregatorV3Interface priceFeed = AggregatorV3Interface(0x8A753747A1Fa494EC906cE90E9f37563A8AF630e);
I checked the address that u used here "0x8A753747A1Fa494EC906cE90E9f37563A8AF630e" found in 4 different chains.
Rinkeby, Kovan, Ropsten, BscScan. Looks like your metamask is connected to Kovan but contract is not deployed to Kovav. Verify which chain your contract is connected and connect to that network in Metamask
Once check the contract is selected correct, If you select AggregationV3Interface contract and deploy it throws this error, select the sol file you are working on and try XD

Custom token showing balance of 0 in MyEtherWallet

I made a new token on the Ropsten test network. Here's the contract address: 0x801fd9c17087ec868dc8540055b7ea3cb6dbbe34.
When I followed the instructions to add this custom token to MyEtherWallet (by specifying the contract address, symbol and correct number of decimals), I see that my ICICB token is added to the token list. However, the balance says 0, even though I have sent some tokens to my address. Also, when I try to select the ICICB token from the dropdown menu to send it, it doesn't show up (just Eth shows up).
When you look at https://ropsten.etherscan.io/address/0x411724F571e83D5fa74d42462F0cAFBddDfed5fc which is my MyEtherWallet address, you can see that is has 2,000,000 ICICB tokens.
Could you please explain to me what's going on? Maybe I'm missing something.
I also, looked at this thread, but it seems to me that my token is ERC20 compliant, as I have all of the necessary functions.
Here's my contract:
pragma solidity ^0.4.24;
// ----------------------------------------------------------------------------
// 'ICICB' token contract
//
// Deployed to : 0x9f7bb2e565F94C3FF3e365eb95cAF73b458b2149
// Symbol : ICICB
// Name : ICICB Token
// Total supply: 100000000
// Decimals : 18
//
// Enjoy.
// (c) by Moritz Neto with BokkyPooBah / Bok Consulting Pty Ltd Au 2017. The MIT Licence.
// ----------------------------------------------------------------------------
// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------
contract SafeMath {
function safeAdd(uint a, uint b) public pure returns (uint c) {
c = a + b;
require(c >= a);
}
function safeSub(uint a, uint b) public pure returns (uint c) {
require(b <= a);
c = a - b;
}
function safeMul(uint a, uint b) public pure returns (uint c) {
c = a * b;
require(a == 0 || c / a == b);
}
function safeDiv(uint a, uint b) public pure returns (uint c) {
require(b > 0);
c = a / b;
}
}
// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
function totalSupply() public view returns (uint);
function balanceOf(address tokenOwner) public view returns (uint balance);
function allowance(address tokenOwner, address spender) public view returns (uint remaining);
function transfer(address to, uint tokens) public returns (bool success);
function approve(address spender, uint tokens) public returns (bool success);
function transferFrom(address from, address to, uint tokens) public returns (bool success);
event Transfer(address indexed from, address indexed to, uint tokens);
event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
//
// Borrowed from MiniMeToken
// ----------------------------------------------------------------------------
contract ApproveAndCallFallBack {
function receiveApproval(address from, uint256 tokens, address token, bytes data) public;
}
// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------
contract Owned {
address public owner;
address public newOwner;
event OwnershipTransferred(address indexed _from, address indexed _to);
constructor() public {
owner = msg.sender;
}
modifier onlyOwner {
require(msg.sender == owner);
_;
}
function transferOwnership(address _newOwner) public onlyOwner {
newOwner = _newOwner;
}
function acceptOwnership() public {
require(msg.sender == newOwner);
emit OwnershipTransferred(owner, newOwner);
owner = newOwner;
newOwner = address(0);
}
}
// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and assisted
// token transfers
// ----------------------------------------------------------------------------
contract ICICBToken is ERC20Interface, Owned, SafeMath {
string public symbol;
string public name;
uint8 public decimals;
uint public _totalSupply;
mapping(address => uint) balances;
mapping(address => mapping(address => uint)) allowed;
// ------------------------------------------------------------------------
// Constructor
// ------------------------------------------------------------------------
constructor() public {
symbol = "ICICB";
name = "ICICB Token";
decimals = 18;
_totalSupply = 100000000000000000000000000;
balances[0x9f7bb2e565F94C3FF3e365eb95cAF73b458b2149] = _totalSupply;
emit Transfer(address(0), 0x9f7bb2e565F94C3FF3e365eb95cAF73b458b2149, _totalSupply);
}
// ------------------------------------------------------------------------
// Total supply
// ------------------------------------------------------------------------
function totalSupply() public view returns (uint) {
return _totalSupply - balances[address(0)];
}
// ------------------------------------------------------------------------
// Get the token balance for account tokenOwner
// ------------------------------------------------------------------------
function balanceOf(address tokenOwner) public view returns (uint balance) {
return balances[tokenOwner];
}
// ------------------------------------------------------------------------
// Transfer the balance from token owner's account to to account
// - Owner's account must have sufficient balance to transfer
// - 0 value transfers are allowed
// ------------------------------------------------------------------------
function transfer(address to, uint tokens) public returns (bool success) {
balances[msg.sender] = safeSub(balances[msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(msg.sender, to, tokens);
return true;
}
// ------------------------------------------------------------------------
// Token owner can approve for spender to transferFrom(...) tokens
// from the token owner's account
//
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// recommends that there are no checks for the approval double-spend attack
// as this should be implemented in user interfaces
// ------------------------------------------------------------------------
function approve(address spender, uint tokens) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
return true;
}
// ------------------------------------------------------------------------
// Transfer tokens from the from account to the to account
//
// The calling account must already have sufficient tokens approve(...)-d
// for spending from the from account and
// - From account must have sufficient balance to transfer
// - Spender must have sufficient allowance to transfer
// - 0 value transfers are allowed
// ------------------------------------------------------------------------
function transferFrom(address from, address to, uint tokens) public returns (bool success) {
balances[from] = safeSub(balances[from], tokens);
allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens);
balances[to] = safeAdd(balances[to], tokens);
emit Transfer(from, to, tokens);
return true;
}
// ------------------------------------------------------------------------
// Returns the amount of tokens approved by the owner that can be
// transferred to the spender's account
// ------------------------------------------------------------------------
function allowance(address tokenOwner, address spender) public view returns (uint remaining) {
return allowed[tokenOwner][spender];
}
// ------------------------------------------------------------------------
// Token owner can approve for spender to transferFrom(...) tokens
// from the token owner's account. The spender contract function
// receiveApproval(...) is then executed
// ------------------------------------------------------------------------
function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);
return true;
}
// ------------------------------------------------------------------------
// Don't accept ETH
// ------------------------------------------------------------------------
function () public payable {
revert();
}
// ------------------------------------------------------------------------
// Owner can transfer out any accidentally sent ERC20 tokens
// ------------------------------------------------------------------------
function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {
return ERC20Interface(tokenAddress).transfer(owner, tokens);
}
}
I looked at all the other relevant threads and I didn't find the answer
The problem was that I used MEW on desktop, and even though I selected the Ropsten testnet on my phone, I needed to select it on my desktop also. This is kinda confusing because the ETH address that was displayed on my desktop version was the Ropsten address (because I switched to it on my phone before scanning the QR code to connect), but for some reason I had to manually set the network on desktop too.
Having the same issue. Ethplorer says I have XYO tokens but it wont show in MEW. I have tried all the different nodes with no luck. I have tried to install the custom token but it says already there. This wallet is a new design from the old style which worked better. Where can I find these tokens which are there hiding in cyberspace.
OK just solved my issue. I am out of the UK at the moment. I used my VPN to connect to the uk. Opened my wallet and there they were. So try using VPN to connect to a different country.

Interacting with a Contract from Another Contract Ethereum

I have a problem which I'm trying to figure out for a week I think I'm 90% there.
If I deploy a contract MerchantA on a private blockchain and retrieve it's contract address and ABI through the solidity command line solc --abi MerchantA.sol and store it.
Where do I enter this ABI & Address in a brand new contract say inside SendMoneyContract method where calls one of the function of AnimalContract deployed at address 0xrandom.
The material I'm finding online has been to include both solidity source code in the same file but for my case, I can't do it. Reason being MerchantAContract is unique for each deployment [each merchant added gets a unique contract`.
So far, from my understanding, I need to include the MerchantA contract address and ABI. I have no idea how to do it inside the solidity function.
You do not do anything with the ABI.
Let's say you want to call the functionA function on MerchantA FROM MerchantB, all you do is take the interface from MerchantA, an example of an interface of an ERC20 token is:
contract Token {
function totalSupply() constant returns (uint256 supply) {}
function balanceOf(address _owner) constant returns (uint256 balance) {}
function transfer(address _to, uint256 _value) returns (bool success) {}
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {}
function approve(address _spender, uint256 _value) returns (bool success) {}
function allowance(address _owner, address _spender) constant returns (uint256 remaining) {}
event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
uint public decimals;
string public name;
}
On MerchantB, wherever you want to call functionA, you put the following code:
MerchantA merchantA = MerchantA(0x0000000000000000000000000000000000000000); //Replace 0x000000000000000000000000000000000000000 with the address of MerchantA
merchantA.functionA();
You will need to swap out the interface of MerchantA because you are not using an ERC20 token as well as what function you want to call.