web3、松露、nodejs 錯誤：UnhandledPromiseRejectionWarning

Question

var     web3            = require('web3'),
    contract        = require('truffle-contract'),
    path            = require('path'),
    MyContractJSON  = require(path.join(__dirname, '../tru_dir/build/contracts/NewCoin.json'));
var     provider        = new web3.providers.HttpProvider("http://localhost:8545");

var     MyContract      = contract(MyContractJSON);

MyContract.setProvider(provider);
MyContract.deployed().then(function(instance){
return instance.returnfive();
})

.then(function(result) {
console.log(result);
}, function(error) {
console.log(error);
});

我將此代碼設置為調用返回 5 的智能合約函數。我使用 truffle 控制台對其進行了測試，並且它工作正常。 但是當嘗試使用 nodejs 獲得相同的結果時，它會崩潰並給出這 2 個錯誤：

(node:6227) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): TypeError: Cannot read property 'apply' of undefined
(node:6227) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

對這個問題有什么想法嗎？

Answer 1

用const MyContract = artifacts.require("MyContractewCoin")替換 MyContract 定義

// You are missing this step before invoking deployer
await deployer.deploy(MyContract) 

const dMyContract = await MyContract.deployed() 
// now you can do stuff like 
let result = await dMyContract.someContractFunction(args)