browser/Test.sol:5:21: TypeError: Definition of base has to precede definition of derived contract contract test is owned ^---^

Question

我遇到了一个我真的不知道如何解决的问题，我正在做一个关于在 solidity 上制作智能合约的教程，以便在以太坊上为未来的大学项目启动。我得到的错误是标题上面的错误。我将复制代码，以便您可以看到我拥有的内容并突出显示错误的代码行。我无法弄清楚问题出在哪里，因为我对类型错误感到模棱两可，而且我是 solidity 的新手。

pragma solidity ^0.4.24;

contract NLtoken is owned
{
    
    uint public totalSupply;
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowence;
    event Transfer (address indexed _from, address indexed _to, uint tokens);
    event Approval (address indexed _tokenOwner, address indexed _spender, uint tokens);
    
    constructor  (string tokenName, string tokenSymbol, uint initialSupply) public {
        totalSupply = initialSupply*10**uint256(decimals);
        balanceOf[msg.sender] = initialSupply;
        name = tokenName;
        symbol = tokenSymbol;
    }
    function _transfer (address _from, address _to, uint256 _value) internal returns(bool success){
       require(_to != 0x0);
        require(balanceOf[_from] >= _value);
        require(balanceOf[_to] + _value >= balanceOf[_to]);
        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;
        emit Transfer(_from, _to, _value);
        return true;
    }
    
    function transfer (address _to, uint256 _value) public returns (bool success)
    {
        _transfer(msg.sender, _to, _value);
        return true;
    }
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)
    {
        require(_value <= allowence[_from][msg.sender]);
        allowence[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
        
    }
    function approve(address _spender, uint256 _value) public returns (bool success)
    {
        allowence[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
        
    }
    function mintToken (address _target, uint256 _mintedAmount) onlyOwner  {
        balanceOf[_target] += _mintedAmount;
        totalSupply += _mintedAmount;
        emit transfer(0, owner, _mintedAmount);
        emit transfer (owner, _target,_mintedAmount);
    }
     function burn (uint256 _value)  onlyOwner returns (bool succes)
    {
        require (balanceOf[msg.sender] >= _value);
        balanceOf[msg.sender] -= _value;
        totalSupply -= _value;
        emit burn(msg.sender, _value);
        return true;
        
    }

        
}
contract owned  {
    
    address public owner;
    constructor ()
    {
        owner = msg.sender;
    }
     modifier  onlyOwner
    {
        require(msg.sender == owner);
        _;
    }
    function transferOwnership(address  newOwner) onlyOwner {
        owner = newOwner;
    }
    
}

Answer 1

在NLtoken合约之前声明拥有合约。请记住，事件名称区分大小写：

emit Transfer(0, owner, _mintedAmount);
emit Transfer (owner, _target,_mintedAmount);

Answer 2

对于遇到此问题的任何其他人，我找到的 none 个答案都特别清楚地说明了问题所在，但上面的 Mad Jackal post 足以让我弄清楚。

在我的例子中，我试图继承的合同引用了另一个合同，该合同导入了第三个单独的合同，在第三个合同中，我也试图继承同样的东西，创建循环依赖查找。

browser/Test.sol:5:21: TypeError: Definition of base has to precede definition of derived contract contract test is owned ^---^

browser/Test.sol:5:21: TypeError: Definition of base has to precede definition of derived contract contract test is owned ^---^

blockchain

ethereum

solidity

smartcontracts

remix