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使用Web3 Ethereum调用智能合约方法

javascriptethereumweb3jsgeth
12

我试图在以太坊上使用区块链技术，但是在尝试与已部署的合约进行接口交互时遇到了问题。我的目标是调用一个方法以显示在本地使用Geth部署的私有区块链中添加的信息。

我无法从我的智能合约中调用任何函数，一直在想我是否做错了什么... 有人能告诉我如何简单地调用此合约中的某个方法吗？比如说，显示现有机构，或者用户所属的机构名称。

我的合约：agency.sol

pragma solidity ^0.4.18;
// We have to specify what version of compiler this code will compile with

contract Agency {

  event NewAgency(uint agencyId, string name, uint dna);

  uint dnaDigits = 16;
  uint dnaModulus = 10 ** dnaDigits;

  //agency structure
  struct Agency {
    string name;
    uint dna;
  }

  Agency[] public agencies;

  mapping (uint => address) public agencyToOwner;
  mapping (address => uint) ownerAgencyCount;

  function _createAgency(string _name, uint _dna) private {
    uint id = agencies.push(Agency(_name, _dna)) - 1;
    agencyToOwner[id] = msg.sender;
    ownerAgencyCount[msg.sender]++;
    NewAgency(id, _name, _dna);
  } 

  function _generateRandomDna(string _str) private view returns (uint) {
    uint rand = uint(keccak256(_str));
    return rand % dnaModulus;
  }

  function createRandomAgency(string _name) public {
    //make sure contract can only execute if user is not part of an agency
    require(ownerAgencyCount[msg.sender] == 0);
    uint randDna = _generateRandomDna(_name);
    _createAgency(_name, randDna);
  }
}

abiDefinition

> abiDefinition
[ { constant: true,
    inputs: [ [Object] ],
    name: 'agencies',
    outputs: [ [Object], [Object] ],
    payable: false,
    stateMutability: 'view',
    type: 'function' },
  { constant: true,
    inputs: [ [Object] ],
    name: 'agencyToOwner',
    outputs: [ [Object] ],
    payable: false,
    stateMutability: 'view',
    type: 'function' },
  { constant: false,
    inputs: [ [Object] ],
    name: 'createRandomAgency',
    outputs: [],
    payable: false,
    stateMutability: 'nonpayable',
    type: 'function' },
  { anonymous: false,
    inputs: [ [Object], [Object], [Object] ],
    name: 'NewAgency',
    type: 'event' } ]

部署成功：

INFO [01-09|19:09:14] Submitted contract creation              fullhash=0x7c43e896329138a6778938ca30d2f5f17f9a63062b359a4fccbd1a1be439f385 contract=0x65175d22C56E1Bad976A331A8B6B448cd4B3995d

最后是contractInstance：

> contractInstance = AgencyContract.at(0x65175d22C56E1Bad976A331A8B6B448cd4B3995d)
Contract {
  _eth: 
   Eth {
     _requestManager: RequestManager { provider: [Object], polls: {}, timeout: null },
     getBalance: { [Function: send] request: [Function: bound ], call: 'eth_getBalance' },
     getStorageAt: { [Function: send] request: [Function: bound ], call: 'eth_getStorageAt' },
     getCode: { [Function: send] request: [Function: bound ], call: 'eth_getCode' },
     getBlock: { [Function: send] request: [Function: bound ], call: [Function: blockCall] },
     getUncle: { [Function: send] request: [Function: bound ], call: [Function: uncleCall] },
     getCompilers: { [Function: send] request: [Function: bound ], call: 'eth_getCompilers' },
     getBlockTransactionCount: 
      { [Function: send]
        request: [Function: bound ],
        call: [Function: getBlockTransactionCountCall] },
     getBlockUncleCount: 
      { [Function: send]
        request: [Function: bound ],
        call: [Function: uncleCountCall] },
     getTransaction: 
      { [Function: send]
        request: [Function: bound ],
        call: 'eth_getTransactionByHash' },
     getTransactionFromBlock: 
      { [Function: send]
        request: [Function: bound ],
        call: [Function: transactionFromBlockCall] },
     getTransactionReceipt: 
      { [Function: send]
        request: [Function: bound ],
        call: 'eth_getTransactionReceipt' },
     getTransactionCount: { [Function: send] request: [Function: bound ], call: 'eth_getTransactionCount' },
     call: { [Function: send] request: [Function: bound ], call: 'eth_call' },
     estimateGas: { [Function: send] request: [Function: bound ], call: 'eth_estimateGas' },
     sendRawTransaction: { [Function: send] request: [Function: bound ], call: 'eth_sendRawTransaction' },
     signTransaction: { [Function: send] request: [Function: bound ], call: 'eth_signTransaction' },
     sendTransaction: { [Function: send] request: [Function: bound ], call: 'eth_sendTransaction' },
     sign: { [Function: send] request: [Function: bound ], call: 'eth_sign' },
     compile: { solidity: [Object], lll: [Object], serpent: [Object] },
     submitWork: { [Function: send] request: [Function: bound ], call: 'eth_submitWork' },
     getWork: { [Function: send] request: [Function: bound ], call: 'eth_getWork' },
     coinbase: [Getter],
     getCoinbase: { [Function: get] request: [Function: bound ] },
     mining: [Getter],
     getMining: { [Function: get] request: [Function: bound ] },
     hashrate: [Getter],
     getHashrate: { [Function: get] request: [Function: bound ] },
     syncing: [Getter],
     getSyncing: { [Function: get] request: [Function: bound ] },
     gasPrice: [Getter],
     getGasPrice: { [Function: get] request: [Function: bound ] },
     accounts: [Getter],
     getAccounts: { [Function: get] request: [Function: bound ] },
     blockNumber: [Getter],
     getBlockNumber: { [Function: get] request: [Function: bound ] },
     protocolVersion: [Getter],
     getProtocolVersion: { [Function: get] request: [Function: bound ] },
     iban: 
      { [Function: Iban]
        fromAddress: [Function],
        fromBban: [Function],
        createIndirect: [Function],
        isValid: [Function] },
     sendIBANTransaction: [Function: bound transfer] },
  transactionHash: null,
  address: 5.771290982673958e+47,
  abi: 
   [ { constant: true,
       inputs: [Array],
       name: 'agencies',
       outputs: [Array],
       payable: false,
       stateMutability: 'view',
       type: 'function' },
     { constant: true,
       inputs: [Array],
       name: 'agencyToOwner',
       outputs: [Array],
       payable: false,
       stateMutability: 'view',
       type: 'function' },
     { constant: false,
       inputs: [Array],
       name: 'createRandomAgency',
       outputs: [],
       payable: false,
       stateMutability: 'nonpayable',
       type: 'function' },
     { anonymous: false,
       inputs: [Array],
       name: 'NewAgency',
       type: 'event' } ],
  agencies: 
   { [Function: bound ]
     request: [Function: bound ],
     call: [Function: bound ],
     sendTransaction: [Function: bound ],
     estimateGas: [Function: bound ],
     getData: [Function: bound ],
     uint256: [Circular] },
  agencyToOwner: 
   { [Function: bound ]
     request: [Function: bound ],
     call: [Function: bound ],
     sendTransaction: [Function: bound ],
     estimateGas: [Function: bound ],
     getData: [Function: bound ],
     uint256: [Circular] },
  createRandomAgency: 
   { [Function: bound ]
     request: [Function: bound ],
     call: [Function: bound ],
     sendTransaction: [Function: bound ],
     estimateGas: [Function: bound ],
     getData: [Function: bound ],
     string: [Circular] },
  allEvents: [Function: bound ],
  NewAgency: { [Function: bound ] 'uint256,string,uint256': [Function: bound ] } }

我尝试过：

contractInstance.agencies()
contractInstance.agencies.call()
contractInstance.agencies.call({from:ak})

导致 Error: Invalid number of arguments to Solidity function

的结果。

contractInstance.agencies.call("name" {from:ak})

结果显示Error: invalid address，我还尝试了调用agencyToOwner和createRandomAgency，但是都没有起作用。

如果您能提供帮助，将不胜感激！

谢谢。

5个回答
21
您可以使用contract.methodName.call()、contract.methodName.sendTransaction()或contract.methodName()方法来调用合约函数。最后一个版本简单地委托给前两个版本之一，具体取决于方法类型（即是否为constant）。请参阅文档中的合约方法部分。
参数列表以函数本身的参数（如果有）开头，然后是可选的事务对象，最后是回调函数。要调用您的createRandomAgency()方法，您需要执行以下操作：
const contract = web3.eth.contract(contractAbi);
const contractInstance = contract.at(contractAddress);

const transactionObject = {
  from: fromAccount,
  gas: gasLimit
  gasPrice: gasPriceInWei
};

contractInstance.createRandomAgency.sendTransaction('name', transactionObject, (error, result) => { // do something with error checking/result here });

交易对象可用选项列表可以在这里找到。

要调用您的公共agencies数组，它看起来像：

contractInstance.agencies.call(0, (error, result) => {
  if (!error) {
    console.log(result.name);
    console.log(result.dna);
  }
}); // transaction object not needed
7
注意：本答案仅适用于web3 1.0之前的版本，在Contract对象中有很多破坏性更改会影响如何调用合约方法。 https://web3js.readthedocs.io/en/1.0/web3-eth-contract.html - WBT
2
我认为你应该尝试这样做-：
 var contractAbi= "" //here put your contract abi in json string
 var deployedContract = web3.eth.contract(abi).at("contract address");
 //now you should be able to access contract methods
 deployedContract.agencies.call({from:address}, function(err,data){
 console.log(data);
 });

试着测试一下。

在执行以下操作后，仍然存在错误：Solidity函数的参数数量无效：var deployedContract = web3.eth.contract(abiDefinition).at("0x65175d22C56E1Bad976A331A8B6B448cd4B3995d");deployedContract.agencies.call({from:web3.eth.accounts[0]},function(err,data){console.log(data);}); - SKYnine
@SKYnine，是的，错误提示是正确的。因为你已经将机构定义为“Agency[] public agencies”。Solidity编译器会生成一个公共getter方法，就像这个例子一样: function agencies(uint256 index)public returns(string, uint); 由于agencies被声明为数组，上述方法实际上需要你将索引作为参数发送。如果你不想这样做，那么你就必须自己定义方法和功能。 - sameepsi
2

现在是2022年，Web3/合约似乎有了一些变化，让我在这里留下一个答案。

假设您正在使用truffle。

步骤1. 创建一个truffle项目，并在本地计算机上安装ganache网络。

步骤2. 创建一个合约并将其部署。获取其地址和网络（例如ganache）。

truffle deploy --network=ganache

步骤3. 运行以下脚本文件：truffle exec call.js --network=ganache

请注意：保留HTML标签，但不要写解释。
// Filename is:  call.js

// you need an address of the contract
const CONTRACT_ADDRESS = "0x7545eCD147210f38EF88142cd94f5Dd0C98E418D"
// you also need the abi of the contract
const contractJson = require('./build/contracts/VeryGoodNftWithMaxSupply.json')


module.exports = async function (callback) {
  // initialize the contract from web3, 
  const contract = new web3.eth.Contract( contractJson.abi, CONTRACT_ADDRESS );

  // get the network
  const network = await web3.eth.net.getNetworkType()

  // call the  `name` method. which is a view method.
  let result = await contract.methods.name().call()
  console.info("name: ", result)  

  // call the `mint` method. which need a TX operation,
  const tx = contract.methods.mint('0xc0dD5021e298dB57bEF361C735cd1C04cef2E48A')

  // send this tx.
  const receipt = await tx
  .send({
    // used first account from your wallet. 
    from: (await web3.eth.getAccounts())[0],
    gas: await tx.estimateGas(),
  })
  .on('transactionHash', (txhash) => {
    console.log(`Mining transaction ... network: ${network}, tx: ${txhash}`)
  })
  .on('error', function(error){
    console.error(`An error happened: ${error}`)
    callback()
  })
  .then(function(receipt){
    // Success, you've minted the NFT. The transaction is now on chain!
    console.log(
        `Success: The NFT has been minted and mined in block ${receipt.blockNumber}`)
    callback()
  })

}

结论

对于"view"函数，应该使用"call"

对于需要tx的函数，应该使用"send"和"once"、"on"

更多详细信息，请查看此演示：https://github.com/sg552/test_erc721_in_truffle_ganache

还请参考：http://siwei.me/blog/posts/blockchain-web3-contract

1

尝试使用回调函数或者Promise。以下代码对我很有用，当我想要从我的合约方法中获取返回值时：

const contract = web3.eth.contract(contractABI);
const contractInstance = contract.at(this.contractAddress);

return new Promise((resolve, reject) => {
  contractInstance.**yourMethod**.call(function (error, result) {
    if (error) {
      console.log(error);
    } else {
      resolve(result);
    }
  });
}) as Promise<number>;

此外，还应查看：https://github.com/ethereum/wiki/wiki/JavaScript-API#using-callbacks。
1
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