DEV Community

Precious Chicken
Precious Chicken

Posted on • Originally published at preciouschicken.com on

Avoiding Call Revert Exception Error when accessing Truffle Ganache via Ethers in Node

#ethereum #truffle #blockchain #node

Introduction

My default way of connecting to a local instance of the Ethereum blockchain using Truffle Ganache is via the browser using Metamask. Using ethers to connect via node.js is however a little different. As the Ethers documentation, at time of writing, contains few specific mentions of Truffle (primarily I suspect as the lead developer doesn't use it), I got a couple of call revert exception errors before I figured out what I was doing wrong.

Setup

Just in case you are completely new to this, some initial set up steps at the terminal:

mkdir justsayhi cd justsayhi truffle init npm init -y npm install ethers
Enter fullscreen mode Exit fullscreen mode

I am assuming you have already installed Node, Truffle and Ganache, if not see my earlier post PreciousChickenToken: A guided example of OpenZeppelin's ERC20 using Ethers, Truffle and React.

Now would also be a good time to fire up Ganache, selecting the Quickstart Ethereum option when offered.

The JavaScript

Create a file node_server.js and copy and paste:

var ethers = require('ethers'); var JustSayHi = require('./build/contracts/JustSayHi.json'); // This is the localhost port Ganache operates on const url = "http://127.0.0.1:7545"; const provider = ethers.providers.getDefaultProvider(url); const contractAddress ='0x02e68a4a2B539451F7d02b166B3376DBc7473F75'; // Connect to the network // We connect to the Contract using a Provider, so we will only // have read-only access to the Contract let contract = new ethers.Contract(contractAddress, JustSayHi.abi, provider); try { contract.sayHi().then(msg => console.log(msg)); } catch (e) { console.log(e); }
Enter fullscreen mode Exit fullscreen mode

The SmartContract

Create a file contracts/JustSayHi.sol and copy and paste:

// SPDX-License-Identifier: Unlicencse pragma solidity ^0.5.1; contract JustSayHi { function sayHi() public pure returns (string memory) { return "Hi"; } }
Enter fullscreen mode Exit fullscreen mode

Create a file migrations/2_deploy_contract.js and copy and paste:

var JustSayHi = artifacts.require("JustSayHi"); module.exports = function(deployer) { // Arguments are: contract deployer.deploy(JustSayHi); };
Enter fullscreen mode Exit fullscreen mode

Deploy the contract

From the terminal run:

truffle deploy
Enter fullscreen mode Exit fullscreen mode

If all good we should get a screen that looks like:

Truffle deploying JustSayHi

Copy the highlighted contract address above and paste it into the contractAddress variable line in node_server.js, which is this line in my example above:

const contractAddress ='0x02e68a4a2B539451F7d02b166B3376DBc7473F75';
Enter fullscreen mode Exit fullscreen mode

Run using Node.js

From the terminal:

node node_server.js
Enter fullscreen mode Exit fullscreen mode

And if all is well you should see a nice, friendly Hi in response.

Configuration

At time of writing I'm using: Truffle v5.1.34 (core: 5.1.34), Solidity v0.5.16 (solc-js), Node v14.4.0, Web3.js v1.2.1, ethers v5.07 and Ubuntu 20.04 LTS.

Top comments (0)