Я пытаюсь разобраться с токенами ERC20 и при попытке создать лотерейный контракт для токена erc20 функция TransferFrom всегда вызывает ошибку, а именно: «Ошибка: требуемый газ превышает допустимый или всегда неуспешная транзакция». Я отделил функцию ApproveDeposit от функции TransferFrom, и функция Approve работала отлично, но функция TransferFrom по-прежнему не работала. есть идеи?
pragma solidity ^0.4.17; import "./IToken.sol"; contract Lottery { address public manager; address[] public players; // the address of the token that is used in the lottery address tokenAddress= 0x3d78a8dfcc300ad8171b695c9b7c5693ab983c78; function Lottery() public { manager = msg.sender; } function approveDeposit(uint amount) private { require(IToken(tokenAddress).approve(this, amount)); } function returnBalance() public view returns(uint){ return IToken(tokenAddress).balanceOf(msg.sender); } function enter(uint256 amount) public{ approveDeposit(amount); require(IToken(tokenAddress).transferFrom(msg.sender, this, amount)); } function random() private view returns (uint) { return uint(keccak256(block.difficulty, now, players)); } function pickWinner() public restricted { // gets token balance of the lottery contract uint contractBalance = IToken(tokenAddress).balanceOf(address(this)); uint index = random() % players.length; //gets psuedo random number and sends to the player at that index IToken(tokenAddress).transfer( players[index], contractBalance); //resets player list players = new address[](0); } modifier restricted() { require(msg.sender == manager); _; } function getPlayers() public view returns (address[]) { return players; } } Вот интерфейс ERC20, который я использую:
pragma solidity ^0.4.19; contract IToken { function totalSupply() public constant returns (uint256 supply) {} function balanceOf(address _owner) public constant returns (uint256 balance) {} function transfer(address _to, uint256 _value) public returns (bool success) {} function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {} function approve(address _spender, uint256 _value) public returns (bool success) {} function allowance(address _owner, address _spender) public constant returns (uint256 remaining) {} event Transfer(address indexed _from, address indexed _to, uint256 _value); event Approval(address indexed _owner, address indexed _spender, uint256 _value); uint public decimals; string public name; } Стив, у тебя контракт с ERC20 неполный, он фактически действует только как интерфейс. Который на самом деле не меняет состояние, но обычно определяет только возврат, проверьте ниже приведенный ниже стандарт токенов от OpenZeeplin.
Я добавил некоторые базовые метрики в конструктор, чтобы создать токен и распространить его по контракту.
Надеюсь, поможет!
pragma solidity ^0.4.24; /** * @title SafeMath * @dev Math operations with safety checks that revert on error */ library SafeMath { /** * @dev Multiplies two numbers, reverts on overflow. */ function mul(uint256 a, uint256 b) internal pure returns (uint256) { // Gas optimization: this is cheaper than requiring 'a' not being zero, but the // benefit is lost if 'b' is also tested. // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522 if (a == 0) { return 0; } uint256 c = a * b; require(c / a == b); return c; } /** * @dev Integer division of two numbers truncating the quotient, reverts on division by zero. */ function div(uint256 a, uint256 b) internal pure returns (uint256) { require(b > 0); // Solidity only automatically asserts when dividing by 0 uint256 c = a / b; // assert(a == b * c + a % b); // There is no case in which this doesn't hold return c; } /** * @dev Subtracts two numbers, reverts on overflow (ie if subtrahend is greater than minuend). */ function sub(uint256 a, uint256 b) internal pure returns (uint256) { require(b <= a); uint256 c = a - b; return c; } /** * @dev Adds two numbers, reverts on overflow. */ function add(uint256 a, uint256 b) internal pure returns (uint256) { uint256 c = a + b; require(c >= a); return c; } /** * @dev Divides two numbers and returns the remainder (unsigned integer modulo), * reverts when dividing by zero. */ function mod(uint256 a, uint256 b) internal pure returns (uint256) { require(b != 0); return a % b; } } /** * @title ERC20 interface * @dev see https://github.com/ethereum/EIPs/issues/20 */ interface IERC20 { function totalSupply() external view returns (uint256); function balanceOf(address who) external view returns (uint256); function allowance(address owner, address spender) external view returns (uint256); function transfer(address to, uint256 value) external returns (bool); function approve(address spender, uint256 value) external returns (bool); function transferFrom(address from, address to, uint256 value) external returns (bool); event Transfer( address indexed from, address indexed to, uint256 value ); event Approval( address indexed owner, address indexed spender, uint256 value ); } contract ERC20 is IERC20 { using SafeMath for uint256; mapping (address => uint256) private _balances; mapping (address => mapping (address => uint256)) private _allowed; uint256 private _totalSupply; string public name; string public sym; uint public decimals; constructor () public { name = "Token"; sym = "TKN"; decimals = 18; _totalSupply = uint(10000000).mul(10**decimals); _balances[msg.sender] = _totalSupply; emit Transfer(address(this), msg.sender, _totalSupply); } /** * @dev Total number of tokens in existence */ function totalSupply() public view returns (uint256) { return _totalSupply; } /** * @dev Gets the balance of the specified address. * @param owner The address to query the balance of. * @return An uint256 representing the amount owned by the passed address. */ function balanceOf(address owner) public view returns (uint256) { return _balances[owner]; } /** * @dev Function to check the amount of tokens that an owner allowed to a spender. * @param owner address The address which owns the funds. * @param spender address The address which will spend the funds. * @return A uint256 specifying the amount of tokens still available for the spender. */ function allowance( address owner, address spender ) public view returns (uint256) { return _allowed[owner][spender]; } /** * @dev Transfer token for a specified address * @param to The address to transfer to. * @param value The amount to be transferred. */ function transfer(address to, uint256 value) public returns (bool) { require(value <= _balances[msg.sender]); require(to != address(0)); _balances[msg.sender] = _balances[msg.sender].sub(value); _balances[to] = _balances[to].add(value); emit Transfer(msg.sender, to, value); return true; } /** * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender. * Beware that changing an allowance with this method brings the risk that someone may use both the old * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards: * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729 * @param spender The address which will spend the funds. * @param value The amount of tokens to be spent. */ function approve(address spender, uint256 value) public returns (bool) { require(spender != address(0)); _allowed[msg.sender][spender] = value; emit Approval(msg.sender, spender, value); return true; } /** * @dev Transfer tokens from one address to another * @param from address The address which you want to send tokens from * @param to address The address which you want to transfer to * @param value uint256 the amount of tokens to be transferred */ function transferFrom( address from, address to, uint256 value ) public returns (bool) { require(value <= _balances[from]); require(value <= _allowed[from][msg.sender]); require(to != address(0)); _balances[from] = _balances[from].sub(value); _balances[to] = _balances[to].add(value); _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value); emit Transfer(from, to, value); return true; } /** * @dev Increase the amount of tokens that an owner allowed to a spender. * approve should be called when allowed_[_spender] == 0. To increment * allowed value is better to use this function to avoid 2 calls (and wait until * the first transaction is mined) * From MonolithDAO Token.sol * @param spender The address which will spend the funds. * @param addedValue The amount of tokens to increase the allowance by. */ function increaseAllowance( address spender, uint256 addedValue ) public returns (bool) { require(spender != address(0)); _allowed[msg.sender][spender] = ( _allowed[msg.sender][spender].add(addedValue)); emit Approval(msg.sender, spender, _allowed[msg.sender][spender]); return true; } /** * @dev Decrease the amount of tokens that an owner allowed to a spender. * approve should be called when allowed_[_spender] == 0. To decrement * allowed value is better to use this function to avoid 2 calls (and wait until * the first transaction is mined) * From MonolithDAO Token.sol * @param spender The address which will spend the funds. * @param subtractedValue The amount of tokens to decrease the allowance by. */ function decreaseAllowance( address spender, uint256 subtractedValue ) public returns (bool) { require(spender != address(0)); _allowed[msg.sender][spender] = ( _allowed[msg.sender][spender].sub(subtractedValue)); emit Approval(msg.sender, spender, _allowed[msg.sender][spender]); return true; } /** * @dev Internal function that mints an amount of the token and assigns it to * an account. This encapsulates the modification of balances such that the * proper events are emitted. * @param account The account that will receive the created tokens. * @param amount The amount that will be created. */ function _mint(address account, uint256 amount) internal { require(account != 0); _totalSupply = _totalSupply.add(amount); _balances[account] = _balances[account].add(amount); emit Transfer(address(0), account, amount); } /** * @dev Internal function that burns an amount of the token of a given * account. * @param account The account whose tokens will be burnt. * @param amount The amount that will be burnt. */ function _burn(address account, uint256 amount) internal { require(account != 0); require(amount <= _balances[account]); _totalSupply = _totalSupply.sub(amount); _balances[account] = _balances[account].sub(amount); emit Transfer(account, address(0), amount); } /** * @dev Internal function that burns an amount of the token of a given * account, deducting from the sender's allowance for said account. Uses the * internal burn function. * @param account The account whose tokens will be burnt. * @param amount The amount that will be burnt. */ function _burnFrom(address account, uint256 amount) internal { require(amount <= _allowed[account][msg.sender]); // Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted, // this function needs to emit an event with the updated approval. _allowed[account][msg.sender] = _allowed[account][msg.sender].sub( amount); _burn(account, amount); } }