Question

我正在使用testrpc，web3 1.0和solidity来构建一个简单的Dapp，但我总是遇到这个错误，我找不到有什么问题。请帮忙。

我的javascript文件：

const Web3 = require('web3');
const fs = require('fs');

const web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

const code = fs.readFileSync('Voting.sol').toString();
const solc = require('solc');
const compiledCode = solc.compile(code);

// deploy contract
const abiDefinition = JSON.parse(compiledCode.contracts[':Voting'].interface);
const VotingContract = new web3.eth.Contract(abiDefinition);
const byteCode = compiledCode.contracts[':Voting'].bytecode;
const deployedContract = VotingContract
.deploy({data: byteCode, arguments: [['a','b','c']]})
.send({
  from: '0x386fd5fbe3804f24b35477f06aa78a178ce021bd',
  gas: 4700000,
  gasPrice: '2000000000'
}, function(error, transactionHash) {})
.on('error', function(error){})
.on('transactionHash', function(transactionHash){})
.on('receipt', function(receipt){
   console.log(receipt.contractAddress);
})
.then(function(newContractInstance) {
  newContractInstance.methods.getList().call({from: '0x386fd5fbe3804f24b35477f06aa78a178ce021bd'}).then(console.log);
});

我的合同文件：

pragma solidity ^0.4.11;
// We have to specify what version of compiler this code will compile with

contract Voting {
  /* mapping field below is equivalent to an associative array or hash.
  The key of the mapping is candidate name stored as type bytes32 and value is
  an unsigned integer to store the vote count
  */

  mapping (bytes32 => uint8) public votesReceived;

  /* Solidity doesn't let you pass in an array of strings in the constructor (yet).
  We will use an array of bytes32 instead to store the list of candidates
  */

  bytes32[] public candidateList;

  /* This is the constructor which will be called once when you
  deploy the contract to the blockchain. When we deploy the contract,
  we will pass an array of candidates who will be contesting in the election
  */
  function Voting(bytes32[] candidateNames) {
    candidateList = candidateNames;
  }

  function getList() returns (bytes32[]) {
    return candidateList;
  }

  // This function returns the total votes a candidate has received so far
  function totalVotesFor(bytes32 candidate) returns (uint8) {
    require(validCandidate(candidate) == false);
    return votesReceived[candidate];
  }

  // This function increments the vote count for the specified candidate. This
  // is equivalent to casting a vote
  function voteForCandidate(bytes32 candidate) {
    require(validCandidate(candidate) == false);
    votesReceived[candidate] += 1;
  }

  function validCandidate(bytes32 candidate) returns (bool) {
    for(uint i = 0; i < candidateList.length; i++) {
      if (candidateList[i] == candidate) {
        return true;
      }
    }
    return false;
  }
}

另外，我正在使用以下命令启动testrpc：

testrpc --account =“0xce2ddf7d4509856c2b7256d002c004db6e34eeb19b37cee04f7b493d2b89306d，2000000000000000000000000000000”

任何帮助将不胜感激。

Answer 1

你不应该使用气体来调用getter方法。请记住，区块链中的读取是免费的 - 写入数据需要花钱（气），因为必须验证写入并达成共识。

因此，您的getter方法应标有constant属性，例如

function getList() constant returns (bytes32[]) {
  return candidateList;
}

其次，您甚至不需要candidateList的getter，因为可以直接访问该属性，例如newContractInstance.candidateList()

第三，您应该使用映射而不是数组，例如mapping(bytes32 => bool) public validCandidates，因为您的合同只关心候选人是否有效。你真的，真的不希望你的合同中有循环，因为你希望你的函数调用具有恒定的燃气成本。如果使用循环，将耗尽气体。

将上述所有内容放在一起就可以获得这样的合同

pragma solidity ^0.4.11;
// We have to specify what version of compiler this code will compile with

contract Voting {
  /* mapping field below is equivalent to an associative array or hash.
  The key of the mapping is candidate name stored as type bytes32 and value is
  an unsigned integer to store the vote count
  */

  mapping (bytes32 => uint8) public votesReceived;
  mapping (bytes32 => bool) public validCandidates;

  /* This is the constructor which will be called once when you
  deploy the contract to the blockchain. When we deploy the contract,
  we will pass an array of candidates who will be contesting in the election
  */
  function Voting(bytes32[] candidateList) {
    for (uint i = 0; i < candidateList.length; i++) {
      validCandidates[candidateList[i]] = true;
    }
  }

  // This function returns the total votes a candidate has received so far
  function totalVotesFor(bytes32 candidate) constant returns (uint8) {
    return votesReceived[candidate];
  }

  // This function increments the vote count for the specified candidate. This
  // is equivalent to casting a vote
  function voteForCandidate(bytes32 candidate) onlyForValidCandidate(candidate) {
    votesReceived[candidate] += 1;
  }

  function isValidCandidate(bytes32 candidate) constant returns (bool)  {
    return validCandidates[candidate];
  }

  modifier onlyForValidCandidate(bytes32 candidate) {
    require(isValidCandidate(candidate));
    _;
  }
}

处理事务时VM异常：缺少气体

1 个答案: