Dapp Introduction

[RCV]

I had a similar issue when you remigrate the people contract the contract address changes so you need to update the

const contractAddress = "0xb4fd34666e8413b732AAA482AAfE60bAF2D82710";

then it should work.

[Bhujanga]

yes, also updating the abi.js file is crucial as well

[dan-i]

Hey @RCV, @Bhujanga

Whenever you deploy a new contract, you need to make sure that you also update the contractAddress in your JS file otherwise your web3 instance will communicate with the wrong contract.

Same thing for the abi, if you change something in your contract (maybe you add or remove a function), you then need to copy and use the new contract abi, otherwise your web3 instance will not know about the changes you made to your contract.

Regards,
Dani

[Bhujanga]

true…true…I found out the hard way, lol

[Elekko]

Hi,

I have some wierd issue here. I’m running ganache and truffle, but when I import one of the accounts from ganache (that has 100 ETH) to Metamask, it shows this balance which I really don’t understand why:

I have also tried, in Ganache to change the chain to Petersburg, Constantinopel etc… but same issue. Anyone one what the issue might be?

Thanks

[KlodyCodez]

Hello. I need help here.
Don’t know what I did wrong but when I press “add data” on the dapp nothing happens. The alert doesn’t come up.

[dan-i]

Hey @Elekko

Is your metamask connected to ganache?
Double check it and share also a print screen of ganache so that we can verify.

Regards,
Dani

[dan-i]

Hi @KlodyCodez

There are syntax errors in your code.
VS code is signalling that with a vertical red mark, check the window.ethereum.enable, you are missing a closing parenthesis.
Try to fix and please post the code here instead of a screenshot so that it’s much faster for us to just copy/paste it.

Cheers,
Dani

[Elekko]

HI dan-i,

I double checked and I see that it is connected, I used the first account in Ganache (I have also tried other). I suspect this is some issue with Ganache? I’m running on Ubuntu 20.04:

[dan-i]

Hey @Elekko

Really strange try to create a new project in Ganache and link your truffle-config from scratch and check again.

Cheers,
Dani

[Elekko]

I did that, same issue. However it works with “truffle develop”, but had to degrade my NodeJS from v14 to v10. Quite pity all this… Might be a bug running Ganache on Ubuntu 20.04

[mervxxgotti]

Hey @dan-i, not sure what I’m doing wrong here but I can’t get the alert in the inputData() function to appear on click. Would you be able to check my code? I have ganache and python server running, and metamask working. Thanks!

var web3 = new Web3(Web3.givenProvider);
var contractInstance;

$(document).ready(function() {
    //brings up metamask ask for permission from browser, then passes accounts in metamask to promise function
    window.ethereum.enable().then(function(accounts) {
      //contract instance of abi template containing function definitions, address of contract, and default sender (metamask account 0)
      contractInstance = new web3.eth.Contract(abi, "0x7961a7dDde5D3B90d4FA4f8c1eA1B62DAE275Ddf", {from: accounts[0]} );
      //console.log(contractInstance);
    });

    $("#add_data_button").click(inputData);
});

function inputData(){
  alert("hello!");
  console.log("hello!");
  /*
  var name = $("#name_input").val();
  var age = $("#age_input").val();
  var height = $("#height_input").val();

  var config {
    value: web3.utils.toWei("1", "ether")
  }

  contractInstance.methods.createPerson(name, age, height).send(config);
  */

}

[mervxxgotti]

@dan-i nevermind Dani, i fixed the problem!

[Daniel01]

Hi Frank,

thanks for the info, I had the same problem.

Daniel

[jonsax]

@filip
I know this is super simple, but I cannot view the contract in the console. I’m getting “Uncaught ReferenceError: Web3 is not defined”. Problem is that it IS DEFINED!

my code for main.js:

var web3 = new Web3(Web3.givenProvider);
var contractInstance;
var abi = [...]

$(document).ready(function() {
    window.ethereum.enable().then((accounts) => {
      contractInstance = new web3.eth.Contract(abi, "0x8e3650Fb6d8BB6142Bc6C5c624fDCFc2Cf9b75E8", { from: accounts[0] });
      console.log(contractInstance);
    });
});

How can I solve this? I have web3.min.js linked in index.html. I’ve also done npm install web3 just because. Please assist!

[jonsax]

figured it out. web3.min.js needed to come BEFORE main.js in the src links in index.html. Just in case anyone else had this issue.

duh…