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02-erc721-2.md

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title actions requireLogin material
Padrão ERC721, Múltipla Herança
verificarResposta
dicas
true
editor
language startingCode answer
sol
zombieownership.sol zombieattack.sol zombiehelper.sol zombiefeeding.sol zombiefactory.sol ownable.sol erc721.sol
pragma solidity ^0.4.19; import "./zombieattack.sol"; // Importe o arquivo aqui // Declare a herança ERC721 aqui contract ZombieOwnership is ZombieAttack { }
pragma solidity ^0.4.19; import "./zombiehelper.sol"; contract ZombieBattle is ZombieHelper { uint randNonce = 0; uint attackVictoryProbability = 70; function randMod(uint _modulus) internal returns(uint) { randNonce++; return uint(keccak256(now, msg.sender, randNonce)) % _modulus; } function attack(uint _zombieId, uint _targetId) external ownerOf(_zombieId) { Zombie storage myZombie = zombies[_zombieId]; Zombie storage enemyZombie = zombies[_targetId]; uint rand = randMod(100); if (rand <= attackVictoryProbability) { myZombie.winCount++; myZombie.level++; enemyZombie.lossCount++; feedAndMultiply(_zombieId, enemyZombie.dna, "zombie"); } else { myZombie.lossCount++; enemyZombie.winCount++; _triggerCooldown(myZombie); } } }
pragma solidity ^0.4.19; import "./zombiefeeding.sol"; contract ZombieHelper is ZombieFeeding { uint levelUpFee = 0.001 ether; modifier aboveLevel(uint _level, uint _zombieId) { require(zombies[_zombieId].level >= _level); _; } function withdraw() external onlyOwner { owner.transfer(this.balance); } function setLevelUpFee(uint _fee) external onlyOwner { levelUpFee = _fee; } function levelUp(uint _zombieId) external payable { require(msg.value == levelUpFee); zombies[_zombieId].level++; } function changeName(uint _zombieId, string _newName) external aboveLevel(2, _zombieId) ownerOf(_zombieId) { zombies[_zombieId].name = _newName; } function changeDna(uint _zombieId, uint _newDna) external aboveLevel(20, _zombieId) ownerOf(_zombieId) { zombies[_zombieId].dna = _newDna; } function getZombiesByOwner(address _owner) external view returns(uint[]) { uint[] memory result = new uint[](ownerZombieCount[_owner]); uint counter = 0; for (uint i = 0; i < zombies.length; i++) { if (zombieToOwner[i] == _owner) { result[counter] = i; counter++; } } return result; } }
pragma solidity ^0.4.19; import "./zombiefactory.sol"; contract KittyInterface { function getKitty(uint256 _id) external view returns ( bool isGestating, bool isReady, uint256 cooldownIndex, uint256 nextActionAt, uint256 siringWithId, uint256 birthTime, uint256 matronId, uint256 sireId, uint256 generation, uint256 genes ); } contract ZombieFeeding is ZombieFactory { KittyInterface kittyContract; modifier ownerOf(uint _zombieId) { require(msg.sender == zombieToOwner[_zombieId]); _; } function setKittyContractAddress(address _address) external onlyOwner { kittyContract = KittyInterface(_address); } function _triggerCooldown(Zombie storage _zombie) internal { _zombie.readyTime = uint32(now + cooldownTime); } function _isReady(Zombie storage _zombie) internal view returns (bool) { return (_zombie.readyTime <= now); } function feedAndMultiply(uint _zombieId, uint _targetDna, string _species) internal ownerOf(_zombieId) { Zombie storage myZombie = zombies[_zombieId]; require(_isReady(myZombie)); _targetDna = _targetDna % dnaModulus; uint newDna = (myZombie.dna + _targetDna) / 2; if (keccak256(_species) == keccak256("kitty")) { newDna = newDna - newDna % 100 + 99; } _createZombie("NoName", newDna); _triggerCooldown(myZombie); } function feedOnKitty(uint _zombieId, uint _kittyId) public { uint kittyDna; (,,,,,,,,,kittyDna) = kittyContract.getKitty(_kittyId); feedAndMultiply(_zombieId, kittyDna, "kitty"); } }
pragma solidity ^0.4.19; import "./ownable.sol"; contract ZombieFactory is Ownable { event NewZombie(uint zombieId, string name, uint dna); uint dnaDigits = 16; uint dnaModulus = 10 ** dnaDigits; uint cooldownTime = 1 days; struct Zombie { string name; uint dna; uint32 level; uint32 readyTime; uint16 winCount; uint16 lossCount; } Zombie[] public zombies; mapping (uint => address) public zombieToOwner; mapping (address => uint) ownerZombieCount; function _createZombie(string _name, uint _dna) internal { uint id = zombies.push(Zombie(_name, _dna, 1, uint32(now + cooldownTime), 0, 0)) - 1; zombieToOwner[id] = msg.sender; ownerZombieCount[msg.sender]++; NewZombie(id, _name, _dna); } function _generateRandomDna(string _str) private view returns (uint) { uint rand = uint(keccak256(_str)); return rand % dnaModulus; } function createRandomZombie(string _name) public { require(ownerZombieCount[msg.sender] == 0); uint randDna = _generateRandomDna(_name); randDna = randDna - randDna % 100; _createZombie(_name, randDna); } }
/** * @title Ownable * @dev The Ownable contract has an owner address, and provides basic authorization control * functions, this simplifies the implementation of "user permissions". */ contract Ownable { address public owner; event OwnershipTransferred(address indexed previousOwner, address indexed newOwner); /** * @dev The Ownable constructor sets the original `owner` of the contract to the sender * account. */ function Ownable() public { owner = msg.sender; } /** * @dev Throws if called by any account other than the owner. */ modifier onlyOwner() { require(msg.sender == owner); _; } /** * @dev Allows the current owner to transfer control of the contract to a newOwner. * @param newOwner The address to transfer ownership to. */ function transferOwnership(address newOwner) public onlyOwner { require(newOwner != address(0)); OwnershipTransferred(owner, newOwner); owner = newOwner; } }
contract ERC721 { event Transfer(address indexed _from, address indexed _to, uint256 _tokenId); event Approval(address indexed _owner, address indexed _approved, uint256 _tokenId); function balanceOf(address _owner) public view returns (uint256 _balance); function ownerOf(uint256 _tokenId) public view returns (address _owner); function transfer(address _to, uint256 _tokenId) public; function approve(address _to, uint256 _tokenId) public; function takeOwnership(uint256 _tokenId) public; }
pragma solidity ^0.4.19; import "./zombieattack.sol"; import "./erc721.sol"; contract ZombieOwnership is ZombieAttack, ERC721 { }

Vamos dar uma olhada no padrão ERC721:

contract ERC721 {
  event Transfer(address indexed _from, address indexed _to, uint256 _tokenId);
  event Approval(address indexed _owner, address indexed _approved, uint256 _tokenId);

  function balanceOf(address _owner) public view returns (uint256 _balance);
  function ownerOf(uint256 _tokenId) public view returns (address _owner);
  function transfer(address _to, uint256 _tokenId) public;
  function approve(address _to, uint256 _tokenId) public;
  function takeOwnership(uint256 _tokenId) public;
}

Esta é a lista de métodos que precisamos implementar, que iremos fazer em partes nos próximos capítulos.

Isso parece um monte, mas sinta-se sobrecarregado! Estamos aqui para guiar você.

Nota: O padrão ERC721 é atualmente um rascunho, e ainda não há oficialmente um acordo de implementação. Neste tutorial usamos a versão atual da biblioteca do OpenZeppelin, mas é possível que mude no futuro antes do lançamento oficial. Então considere esta uma possível implementação, mas não considere uma versão oficial dos tokens ERC721.

Implementando um contrato de token

Quando implementar um contrato de token, a primeira coisa que fazemos é copiar a interface para o nosso próprio arquivo Solidity e importá-lo. import "./erc721.sol";. Então nós teremos o nosso contrato herdando-o, e iremos sobrepor cada método com a definição da função.

Mas espere – ZombieOwnership já esta herdando do ZombieAttack – como pode também herdar do ERC721?

Para a nossa sorte em Solidity, seu contrato pode herdar de múltiplos contrato conforme segue:

contract SatoshiNakamoto is NickSzabo, HalFinney {
  // Meu deus, os segredos do universo foram revelados!
}

Como você pode ver, quando usando a múltipla herança, você pode separar os múltiplos contrato que você estar herdando com um vírgula, ,. Neste caso, nosso contrato esta herdando de NickSzabo e HalFinney.

Vamos testar

Já criamos erc721.sol com as interfaces acima para você.

  1. Importe o erc721.sol em zombieownership.sol

  2. Declare o ZombieOwnership herdando de ZombieAttack e ERC721