功能代码未调用正确的令牌地址，而是在调用正确的功能

Question

我正在尝试调用已部署合同的批准功能。我正在获取实际的函数来回溯并且金额和合同正确，但是我没有获得正确的批准功能来链接到令牌。它只是尝试批准发送一个空令牌。

我尝试将功能与某个地址相关联，但无法这样做。

pragma solidity >=0.4.22 <0.6.0;
    contract Deployed {
        mapping (address => mapping (address => uint256)) public allowance;
        event Approval(address indexed _owner, address indexed _spender, uint256 _value);
        function approve(address _spender, uint256 _value) public returns (bool arbitrary) {
            allowance[msg.sender][_spender] = _value;
            emit Approval(msg.sender, _spender, _value);
            return true;
        }
    }
    contract Existing  {
        Deployed dc;
        constructor(address _t) public {dc = Deployed(_t);}
        function approve(address _spender, uint256 _value) public returns (bool) {
            return dc.approve(_spender, _value);
        }
    }

我只希望批准功能引用实际部署的合同。