Problem with array of adresses

Question

I have following code of my smart contract, it has simple problem:

browser/Referrals.sol:100:35: TypeError: Type function (uint256) pure returns (address[] memory) is not implicitly convertible to expected type address[] storage ref. ReferralsOf[msg.sender] = new address[];

Can you explain how can I solve this problem.

library SafeMath 
{
    function add(uint a, uint b) internal pure returns (uint c)
    {
        c = a + b;
        require(c >= a);
    }
    function sub(uint a, uint b) internal pure returns (uint c) 
    {
        require(b <= a);
        c = a - b;
    }
    function mul(uint a, uint b) internal pure returns (uint c) 
    {
        c = a * b;
        require(a == 0 || c / a == b);
    }
    function div(uint a, uint b) internal pure returns (uint c)
    {
        require(b > 0);
        c = a / b;
    }
}

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);
    }
}

contract ReferraledToken is Owned
{
    using SafeMath for uint;
    string public symbol;
    string public  name;
    uint8 public decimals;
    uint _totalSupply;
    uint64 current = 100000;
    mapping(address => uint) balances;
    mapping(address => address) ReferralOf;
    mapping(address => address[]) ReferralsOf;
    mapping(address => uint64) ReferralLink;
    mapping(uint64 => address) LinkOf;
    mapping(address => bool) registeredUser;

    constructor() public {
        symbol = "LETO";
        name = "IT project";
        decimals = 5;
        _totalSupply = 1000000 * (10 ** uint(decimals));
        balances[owner] = _totalSupply;
    }

    function totalSupply() public view returns (uint)
    {
        return balances[owner];
    }
    function balanceOf(address tokenOwner) public view returns (uint balance)
    {
        return balances[tokenOwner];
    }
    function transfer(address to, uint tokens) public returns (bool success) {
        balances[msg.sender] = balances[msg.sender].sub(tokens);
        balances[to] = balances[to].add(tokens);
        return true;
    }
    function sendPurchaseToken(address to) payable public returns (bool) 
    {
        balances[owner] = balances[owner].sub(uint(decimals) * msg.value / 10);
        balances[to] = balances[to].add(uint(decimals) * msg.value / 10);
        return true;
    }
    function registerUser(uint64 _code) public
    {
        require(registeredUser[msg.sender] == false);
        ReferralOf[msg.sender] = LinkOf[_code]; 
        ReferralsOf[LinkOf[_code]].push(msg.sender);
        ReferralLink[msg.sender] = current;
        LinkOf[ReferralLink[msg.sender]] = msg.sender;
        ReferralsOf[msg.sender] = new address[];
        current += 1;
    }
    function lengthOfPath(address _start, uint _counter) public returns (uint)
    {
        if (ReferralOf[_start] != owner)
        {
            return lengthOfPath(ReferralOf[_start], _counter + 1);
        }
        else
        {   
            return _counter;
        }
    }

}

Answer 1

new address[] returns a new array of addresses in memory. You can't then assign that to ReferralsOf[msg.sender] because there's no built-in support for such an array copy operation.

Fortunately, you probably don't need to do it at all. You probably meant to set registeredUser[msg.sender] to true somewhere in that function. If you do that, you don't have to worry about reusing ReferralsOf[msg.sender], so there's no need to do anything. (The array in that struct is already empty.)

But if you want to be doubly safe, you can use delete ReferralsOf[msg.sender] or ReferralsOf[msg.sender].length = 0 to empty the array if it already has data in it.