solidity 文法學習

標籤：port   using   否則   factor   方法   ready   balance   change   繼承   

基於 cryptozombies.ioZombieFactory

pragma solidity ^0.4.19;contract ZombieFactory {    // 事件， web3.js 可以監控它    event NewZombie(uint zombieId, string name, uint dna);    uint dnaDigits = 16;    uint dnaModulus = 10 ** dnaDigits; // 乘方    // 定義結構體    struct Zombie {        string name;        uint dna;    }    // 定義數組    Zombie[] public zombies;    // 定義 mapping 結構， 可理解為 python 裡面的 dict    mapping (uint => address) public zombieToOwner;    mapping (address => uint) ownerZombieCount;    function _createZombie(string _name, uint _dna) internal {        uint id = zombies.push(Zombie(_name, _dna)) - 1; // 擷取剛剛放到數組的元素的 id                // msg.sender 為調用者的 地址。        zombieToOwner[id] = msg.sender;         ownerZombieCount[msg.sender]++;                // 觸發事件        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 {            // 要求每個賬戶只能有一隻殭屍，否則退出        require(ownerZombieCount[msg.sender] == 0);                uint randDna = _generateRandomDna(_name);        randDna = randDna - randDna % 100;        _createZombie(_name, randDna);    }}

學到了

• 函數的定義
• 數組的使用
• mapping 的使用
• require的使用
• 事件的使用

ZombieFeeding

pragma solidity ^0.4.19;import "./zombiefactory.sol";// 定義一個合約介面，通過這種方式可以調用其他合約的公開方法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  );}// 繼承contract ZombieFeeding is ZombieFactory {  KittyInterface kittyContract;  // 使用了函數修飾符，確保只有 合約賬戶本身可以調用該方法  function setKittyContractAddress(address _address) external onlyOwner {    // 通過 合約地址執行個體化介面，以後可以通過這個介面調用該合約的方法    kittyContract = KittyInterface(_address);   }  // 傳輸結構體指標  function _triggerCooldown(Zombie storage _zombie) internal {    _zombie.readyTime = uint32(now + cooldownTime);  }  // 返回 bool 類型  function _isReady(Zombie storage _zombie) internal view returns (bool) {      return (_zombie.readyTime <= now);  }  function feedAndMultiply(uint _zombieId, uint _targetDna, string species) internal {    require(msg.sender == zombieToOwner[_zombieId]);    Zombie storage myZombie = zombies[_zombieId];    require(_isReady(myZombie));    _targetDna = _targetDna % dnaModulus;    uint newDna = (myZombie.dna + _targetDna) / 2;    if (keccak256(species) == keccak256("kitty")) { // if 語句的使用      newDna = newDna - newDna % 100 + 99;    }    _createZombie("NoName", newDna);    _triggerCooldown(myZombie);  }  function feedOnKitty(uint _zombieId, uint _kittyId) public {    uint kittyDna;    // 調用其他合約的方法    (,,,,,,,,,kittyDna) = kittyContract.getKitty(_kittyId);  // 多個傳回值的擷取        feedAndMultiply(_zombieId, kittyDna, "kitty");  }}

學到了

• 調用其他合約的方法
• 結構體傳值
• 接收多個傳回值的方法
• 函數修飾符的使用

ZombieHelper

pragma solidity ^0.4.19;import "./zombiefeeding.sol";contract ZombieHelper is ZombieFeeding {  uint levelUpFee = 0.001 ether;  // 定義修飾函數，會在被修飾函數調用前調用  modifier aboveLevel(uint _level, uint _zombieId) {    // 如果指定殭屍的 level 小於 _level 就會退出，否則繼續執行被修飾的函數    require(zombies[_zombieId].level >= _level);    _;  }  // 用於提出 以太坊裡面的 eth  function withdraw() external onlyOwner {    owner.transfer(this.balance);  }  //   function setLevelUpFee(uint _fee) external onlyOwner {    levelUpFee = _fee;  }  // payable 修飾符表示，可以往這個方法發送 eth  function levelUp(uint _zombieId) external payable {    require(msg.value == levelUpFee);  // 判斷 eth 的值    zombies[_zombieId].level++;  }  // 使用了修飾符，當層級大於 2 時才能修改名字  function changeName(uint _zombieId, string _newName) external aboveLevel(2, _zombieId) {    require(msg.sender == zombieToOwner[_zombieId]);    zombies[_zombieId].name = _newName;  }  function changeDna(uint _zombieId, uint _newDna) external aboveLevel(20, _zombieId) {    require(msg.sender == zombieToOwner[_zombieId]);    zombies[_zombieId].dna = _newDna;  }  // 返回一個列表  function getZombiesByOwner(address _owner) external view returns(uint[]) {       // 定義 memory 數組，節省 gas    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;  }}

學到了

• 定義修飾函數，以及往修飾函數傳參
• 接收，提取 eth
• 返回 uint[]
• memory 變數， for 迴圈的使用

後面接著又瞭解了 SafeMath 的使用

pragma solidity ^0.4.19;import "./zombieattack.sol";import "./erc721.sol";import "./safemath.sol";contract ZombieOwnership is ZombieAttack, ERC721 {  using SafeMath for uint256;  mapping (uint => address) zombieApprovals;  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 _from, address _to, uint256 _tokenId) private {    ownerZombieCount[_to] = ownerZombieCount[_to].add(1);    ownerZombieCount[msg.sender] = ownerZombieCount[msg.sender].sub(1);    zombieToOwner[_tokenId] = _to;    Transfer(_from, _to, _tokenId);  }  function transfer(address _to, uint256 _tokenId) public onlyOwnerOf(_tokenId) {    _transfer(msg.sender, _to, _tokenId);  }  function approve(address _to, uint256 _tokenId) public onlyOwnerOf(_tokenId) {    zombieApprovals[_tokenId] = _to;    Approval(msg.sender, _to, _tokenId);  }  function takeOwnership(uint256 _tokenId) public {    require(zombieApprovals[_tokenId] == msg.sender);    address owner = ownerOf(_tokenId);    _transfer(owner, msg.sender, _tokenId);  }}

solidity 文法學習