从 web3-1.0.0-beta.27 获取 Solidity 合约函数的 return 值

Question

我是运行web3 1.0.0-beta.27, 编译指示 solidity ^0.4.2;

contract Charity{

    function ping() public constant returns (uint) {
        return 200;
    }


}

我 compiling/calling 它在 typescript 中有：

import * as fs       from 'fs'       ;
import * as solc     from 'solc'     ;
import * as Web3     from 'web3'     ; 


var web3   = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));

var contract_path : string = "path/to/Charity.sol"
const input       = fs.readFileSync(contract_path)
const output      = solc.compile(input.toString(), 1);
var contract_name = ":" + pr.last(contract_path.split("/")).split(".")[0]
const bytecode    = output.contracts[contract_name].bytecode
const abi_        = JSON.parse(output.contracts[contract_name].interface);

web3.eth.getAccounts().then(accounts => {

    var coinbase = accounts[0];
    var receiver = accounts[1];

    // create contract
    var myContract = new web3.eth.Contract([], {
          from     : coinbase
        , gasPrice : '20000000000'
    });

    // set address to coinbase, and jsonInterface to abi
    myContract.options.address = coinbase;
    myContract.options.jsonInterface = abi_;

    // deploy contract -> problem, how do I get the abi in here?
    var deployedContract = myContract.deploy({

        data: '0x' + bytecode,

    }).send({

        from: coinbase,
        gas : 1500000 ,
        gasPrice: '30000000000000'            

    }, (err, hash) => {

        if (err) { console.log("error on deployment: ", err) }
        console.log("Hash: ", hash)
    })

    // send contract fn to network to be executed
    // problem: this is not doing what it's suppose to 
    myContract.methods.ping().send({ from : coinbase }, (err, val) => {
        console.log("ping(): ", err, val)
    })

    myContract.methods.ping().send({from: coinbase})
    .on('transactionHash', function(hash){
        console.log("hash: ", hash)
    })
    .on('receipt', function(receipt){
        console.log("recepit: ", receipt)
    })
    .on('confirmation', function(confirmationNumber, receipt){
        console.log("conffirmation: ", receipt)
    })
    .on('error', console.error);        



});

问题是 myContract.methods.ping().send... 没有按照我的要求在回调中返回值 200，有没有办法解决这个问题？

Answer 1

调用常量函数后，应使用 call() 而不是 send() 方法。

查看文档： http://web3js.readthedocs.io/en/1.0/web3-eth-contract.html#methods-mymethod-call

Answer 2

当您不修改状态时，您只需使用 call()。如果你修改状态，你需要一个交易（发送），然后你需要等待交易被挖掘。何时执行此操作是发出事件并监听它。

从 web3-1.0.0-beta.27 获取 Solidity 合约函数的 return 值

Getting return value of Solidity contract function from web3-1.0.0-beta.27

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