Skip to content

Latest commit

 

History

History
339 lines (257 loc) · 11.1 KB

03-erc721-3.md

File metadata and controls

339 lines (257 loc) · 11.1 KB
title actions requireLogin material
balanceOf と ownerOf
答え合わせ
ヒント
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"; import "./erc721.sol"; contract ZombieOwnership is ZombieAttack, ERC721 { function balanceOf(address _owner) public view returns (uint256 _balance) { // 1.ここで`_owner`がもつゾンビの数を返すのだ } function ownerOf(uint256 _tokenId) public view returns (address _owner) { // 2. `_tokenId`の所有者をここで返すのだ } 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 "./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 { function balanceOf(address _owner) public view returns (uint256 _balance) { return ownerZombieCount[_owner]; } function ownerOf(uint256 _tokenId) public view returns (address _owner) { return zombieToOwner[_tokenId]; } function transfer(address _to, uint256 _tokenId) public { } function approve(address _to, uint256 _tokenId) public { } function takeOwnership(uint256 _tokenId) public { } }

よくできた、ではERC721の実装に入っていくぞ!

中身は空のままだが、我々はこのレッスンで実装する全ての関数を写し書いてきた。

このチャプターではまずbalanceOfownerOfの2つのメソッドを実装していこう。

balanceOf

  function balanceOf(address _owner) public view returns (uint256 _balance);

この関数は単にaddressを受け取り、そのaddressのトークン保有量を返す。

我らの場合、『トークン』はゾンビだ。このDAppsで所有者のゾンビ保有数をどこに保存しているか覚えているか?

ownerOf

  function ownerOf(uint256 _tokenId) public view returns (address _owner);

この関数はトークンID (この場合ゾンビのIDだ)を受け取り、その所有者の addressを返す。

このDAppにはすでにこの情報を格納している mappingがあるから、実装はとても簡単だ。この関数はreturnステートメントの1行で実装できる。

注: uint256uintに相当すると覚えておいてください。これまでコード中uintを用いてきましたが規格からコピー&ペーストしているので、ここではuint256を使用しています。

さあテストだ

これら2つの関数の実装方法を理解しよう。

各関数はシンプルにreturnステートメントのコード1行だけにするのだ。このデータをどこで保存しているか、前のレッスンを見てみるといいぞ。もしわからなければ、『答えを見る』ボタンでヒントを得ても良いからな。

  1. balanceOfを実装し、_ownerのゾンビ保有数を返すようにせよ。

  2. ownerOfを実装し、_tokenIdをIDに持つゾンビを保有する者のアドレスを返せ。.