Solidity
使用虛擬和覆蓋的繼承問題（可能）：找不到成員
我正在嘗試完成一門涵蓋虛擬和覆蓋的課程，並且似乎由於繼承而出現錯誤。下面是程式碼：
//SPDX-License-Identifier: GPL-3.0 pragma solidity >=0.5.0 <0.9.0; // ------------------------------------------------------------- // EIP-20: ERC-20 Token Standard // https://eips.ethereum.org/EIPS/eip-20 // ------------------------------------------------------- interface ERC20Interface { // these three are only mandatory functions function totalSupply() external view returns (uint); function balanceOf(address tokenOwner) external view returns (uint balance); function transfer(address to, uint tokens) external returns (bool success); function allowance(address tokenOwner, address spender) external view returns (uint remaining); function approve(address spender, uint tokens) external returns (bool success); function transferFrom(address from, address to, uint tokens) external returns (bool success); event Transfer(address indexed from, address indexed to, uint tokens); event Approval(address indexed tokenOwner, address indexed spender, uint tokens); } // our contract will inherit from the standard token interface contract Pennies is ERC20Interface { string public name = "Penny Pennies"; string public symbol = "PENNY"; uint public decimals = 0; // 18 is the most // need to override the inherited mandatory function uint public override totalSupply; // not part of standard address public founder; // this is how the contract stores the balance for each address mapping (address => uint) public balances; // this is a nested mapping (points to another mapping // shows how much one user allows the other user to spend // allower address is entered that points to mapping of addresses // and how much they are allowed to spend mapping(address => mapping(address => uint)) allowed; constructor(){ // set initial supply totalSupply = 1000000; // set founder as person who deploys contract founder = msg.sender; // set the balance of the founder's address equal to the total supply balances[founder] = totalSupply; } // we need to override the balance function function balanceOf(address tokenOwner) public view override returns (uint balance){ return balances[tokenOwner]; } // we need to override the transfer function function transfer(address to, uint tokens) public virtual override returns (bool success){ // the balance of the sender must be at least as much as they want to send require(balances[msg.sender] >= tokens); // the balance for the recipient's address increases balances[to] += tokens; // the balances for the sender's address decreases balances[msg.sender] -= tokens; // emit our event of the actual transfer emit Transfer(msg.sender, to, tokens); // returns status return true; } // this overrides our allowed function and returns how much eash user is allowed to // spend by the token owner function allowance(address tokenOwner, address spender) public view override returns (uint){ return allowed[tokenOwner][spender]; } function approve(address spender, uint tokens) public override returns (bool success){ // the sender has to have at least the amount of tokens they want to approve require(balances[msg.sender] >= tokens); // can't be an empty transaction require(tokens > 0); // updates allowed mapping so that the spender is allowed to spend a // certain amount of tokens allowed[msg.sender][spender] = tokens; // emit approval transaction emit Approval(msg.sender, spender, tokens); // return state return true; } function transferFrom(address from, address to, uint tokens) public virtual override returns (bool){ // require that the user be allowed to send the amount of tokens desired require(allowed[from][msg.sender] >= tokens); // require they have the amount of tokens they want to transfer require(balances[from] >= tokens); // subtract token balance from user's balance balances[from] -= tokens; // subtract sent amount from total allowed amount allowed[from][msg.sender] -= tokens; // add tokens to balance of recipient balances[to] += tokens; // emit tranfer emit Transfer(from, to, tokens); // return status return true; } } // ICO Contract contract PennyICO is Pennies { // declare admin address public admin; // declare deposit vault address payable public deposit; // set token price uint tokenPrice = 0.000001 ether; // hard cap of total ether that can be invested uint public hardCap = 300 ether; // value in wei of raised amount uint public raisedAmount; // start time uint public saleStart = block.timestamp + 10; // set ICO close time (1 week) uint public saleEnd = block.timestamp + 3600 * 24 * 7; // tokens will be transferred to investor wallets // one week after the ICO ends uint public tokenTradeStart = saleEnd + 604800; // set max and min investment per address uint public maxInvestment = 5 ether; uint public minInvestment = 0.00001 ether; // create an enum to hold the state of our ICO enum State {beforeStart, running, afterEnd, halted} // declare a state variable of type state to hold the ICO state State public ICOstate; // declare constructor of contract constructor(address payable _deposit){ deposit = _deposit; admin = msg.sender; ICOstate = State.beforeStart; } // admin should be able to halt ICO in emrgency // first make admin modifier modifier onlyAdmin(){ require(msg.sender == admin); _; } // admin can halt ICO function halt() public onlyAdmin{ ICOstate = State.halted; } // admin can resume ICO function resume() public onlyAdmin{ ICOstate = State.running; } // function to allow the admin to change the deposit contract function changeDepositAddress(address payable newDeposit) public onlyAdmin{ deposit = newDeposit; } // a getter function to return the state of the ICO function getCurrentState() public view returns(State){ if (ICOstate == State.halted){ return State.halted; } else if (block.timestamp < saleStart){ return State.beforeStart; } else if (block.timestamp >= saleStart && block.timestamp <= saleEnd){ return State.running; } else { return State.afterEnd; } } // to make the below function interact with front end we create an event event Invest(address investor, uint value, uint tokens); // main function for ICO function invest() payable public returns(bool){ // first we need to establish that ICO is currently running ICOstate = getCurrentState(); // test if ICO is running require(ICOstate == State.running); // must invest in the limits for per address investment range require(msg.value >= minInvestment && msg.value <= maxInvestment); // increment raised amount raisedAmount += msg.value; // make sure ICO hardcape won't already be breached require(raisedAmount <= hardCap); // calculate number of tokens the user has bought uint tokens = msg.value / tokenPrice; // exchange tokens between founder and investor balances[msg.sender] += tokens; balances[founder] -= tokens; // send investor's wei to deposit vault deposit.transfer(msg.value); // emit event for frontend emit Invest(msg.sender, msg.value, tokens); // return transaction state return true; } // create template receivable function that calls the invest function // above if the user sends money directly to the address receive() payable external{ invest(); } // we need to override the transfer function again to let the user be able // to trade it a week after receiving it function transfer(address to, uint tokens) public override returns (bool success){ // require the trading holding persiod has passed require(block.timestamp > tokenTradeStart); // transfer the tokens to the recipient Pennies.tranfer(to, tokens); // return function status return true; } function transferFrom(address from, address to, uint tokens) public override returns (bool){ require(block.timestamp > tokenTradeStart); Pennies.transferFrom(from, tokens); return true; } }
Pennies.transfer當我嘗試或時似乎找不到“便士”Pennies.transferFrom。
我注意到第 277 行有一個錯字，應該是：（
Pennies.transfer(to, tokens);缺少 s）。同樣在第 287 行，
Pennies.transferFrom缺少to參數，應替換為：Pennies.transferFrom(from, to, tokens);除此之外，程式碼工作正常。我建議您使用 IDE 輕鬆調試此類錯誤。無需設置即可使用的最簡單的方法是https://remix.ethereum.org