Withdraw balance from external contract in Solidity 0.6

Question

Getting two errors with the following code.

abstract contract ReceiveBalanceContract is Ownable {

    receive() external payable {
        require(msg.sender == address(SendBalanceContract));
    }

    function withdrawBalance() external {

        owner.call.value(address(this).balance)();
    }
}

contract SendBalanceContract {

    constructor(address _nftAddress) public {

        ERC721 candidateContract = ERC721(_nftAddress);
        require(candidateContract.supportsInterface(InterfaceSignature_ERC721)); 
        nonFungibleContract = candidateContract;
    }

    function withdrawBalance() external {
        address nftAddress = address(nonFungibleContract);

        require(msg.sender == owner || msg.sender == nftAddress); // Error 1
        bool res = nftAddress.call.value(address(this).balance)(""); // Error 2
    }
}

I am getting two errors and can't manage to fix this. Error 1:

TypeError: Operator == not compatible with types address payable and function () view returns (address)
require(msg.sender == owner || msg.sender == nftAddress);

Error 2:

TypeError: Different number of components on the left hand side (1) than on the right hand side (2).

I don't understand what s going on here

Answer 1

Down below is the correct code and my mistakes were due to: call.value returns two value (bool, bytes memory) (not just bool) and the new Ownable contract has no public access variable owner anymore, but instead a function owner() to get the address of contract owner.

pragma solidity ^0.6.0;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/ERC721.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/introspection/ERC165Checker.sol";

abstract contract ReceiveBalanceContract is Ownable, ERC721 {

    SendBalanceContract public saleAuction;

    receive() external payable {
        address auctionContract = address(saleAuction);
        require(msg.sender == auctionContract);
    }

    function withdrawBalance() external {

        owner().call{value: address(this).balance}("");
    }
}

contract SendBalanceContract is Ownable {

    using ERC165Checker for address; // pm added librairy. Not sure this is address

    ERC721 public nonFungibleContract;

    bytes4 constant InterfaceSignature_ERC721 = bytes4(0x9a20483d);

    constructor(address _nftAddress) public {

        ERC721 candidateContract = ERC721(_nftAddress);
        require(candidateContract.supportsInterface(InterfaceSignature_ERC721)); 
        nonFungibleContract = candidateContract;
    }

    function withdrawBalance() external {
        address nftAddress = address(nonFungibleContract);

        require(msg.sender == owner() || msg.sender == nftAddress);
        // We are using this boolean method to make sure that even if one fails it will still work
        (bool sent, bytes memory data) = nftAddress.call{value:address(this).balance}("");
    }
}