Why can't I use a contract method in my Chrome console?

Question

I am attempting to call a method from a smart contract from my chrome console. My dApps index.html file is deployed locally at http://127.0.0.1:5500.

I set up web3 and instantiate a smart contract with the following code:

window.addEventListener('load', async () => {
    if (typeof web3 !== 'undefined') {
        web3 = new Web3(web3.currentProvider);
        console.log('metamask success');
        await window.ethereum.enable();
        web3.eth.defaultAccount = web3.eth.accounts.givenProvider.selectedAddress;

    } else { // I removed this code for brevity


abi = [ { constant: false, ... // I removed the full abi for conciseness

MyContract = web3.eth.contract(abi);

contractInstance = MyContract.at("0xd01e06f2e70bea9ae7640367bdf0b24ac5f35ed1");

I can successfully make the following transaction from my console in Google Chrome:

web3.eth.sendTransaction({value: web3.utils.toWei('.1'), to: "0x493b6DEb52B40A517Fa64f580B5bfd325537764E"}, (e,r) =>{console.log(e,r)})

But when I try an make the following transaction:

contractInstance.notarize(item, (e,r) => {console.log(e,r)})

I get the following error message in my Chrome console:

Uncaught TypeError: Cannot read property 'match' of undefined

Any ideas on what is going on here?

Answer 1

Methods of a contract can be accessed by methods method of a contract instance. And the transaction can be either called by call() method or sent by send() method.

So, you should use smth like that:

contractInstance.methods.notarize(item).send((e,r) => {console.log(e,r)})

See more info in the web3js documentation.

Answer 2

What is the ABI for your contract? That is, how many arguments does the notarize method take and of what type?

Usually a call to a method in web3 takes arguments like methodName(arg1, arg2, ..., argn, { from: '0xblah', gas: '0xblah', ... }, callbackFunc)