Calling function from another upgradable proxy smart contract

Question

I have 2 diffrent NFT collection. They are both transparentUpgradableProxy smart contracts. I used to call another function like this before I upgraded them to transparentUpgradableProxy.

function mint(uint256 tokenId) public payable {
   IERC721 token = IERC721(mainContractAddress);
   uint256 ownedAmount = token.balanceOf(msg.sender);
   require((ownedAmount / requiredNftAmountFirstStage) - claimedAmountFirstStage[msg.sender] > 0, "You are not eligible for free NFT!");
   require(ownerOf(tokenId) == address(0), "NFT already claimed!");

   _safeMint(msg.sender, tokenId);
   claimedAmountFirstStage[msg.sender] += 1;
}

After I changed it to transparentUpgradableProxy, I tried to do it like this:

IERC721Upgradeable token = IERC721Upgradeable(mainContractAddress);
uint256 ownedAmount = token.balanceOf(msg.sender);

Im guessing this is not how it works. How can I access to another upgradable smart contracts function?

Thanks!

edit1: I cant use delegatecall because it says its unsafe. My both smart contract is upgradableProxy. I tried to do it will call, which returns bool and bytes.

    IERC721Upgradeable token = IERC721Upgradeable(mainContractAddress);
    (bool success, bytes memory result) = address(token).call(abi.encodeWithSignature("balanceOf(address)", msg.sender));
    require(success);
    uint256 ownedAmount = toUint256(result);

Still not working :( My other question is, I need to call that function from proxy smart contract right?

Answer 1

You would use delegatecall() with encoding with a function signature:

uint256 ownedAmount = token.delegatecall(abi.encodeWithSignature("balanceOf(address)", msg.sender)

Answer 2

    (bool success, bytes memory result) = address(mainContractAddress).call(abi.encodeWithSignature("balanceOf(address)", msg.sender));
    require(success, "Failed to get balance...");
    uint256 ownedAmount = toUint256(result);

Delegatecall cant be use because of safety issues but call works fine. Im calling this from my second logic contract to main proxy address. It returns bool and bytes. Bytes can be transfromed into uint with some libraries.