Metamask issues: unable to call methods from contract in React JS app

As a developer working on a React.js application using Solidity, Ganache, Truffle, and React, you may encounter an issue where you cannot call methods from your contract. This problem is quite common when using Metamask as a wallet provider for Ethereum smart contracts.

Background Information

In a typical React.js application, you can interact with a smart contract through its ABI (Application Binary Interface) or the web3 library. However, when using Metamask as a wallet provider, things get more complicated. Metamask is an Ethereum-compatible wallet that allows users to securely store and manage their private keys.

Problem: Unable to call methods from contract

When you try to call a method from your contract using Web3 or another library, you may encounter the following error:

TypeError: Cannot call method 'call' on instance of Contract

This error occurs when Metamask tries to call a method that is not in the ABI of the contract.

Debug Steps

To resolve this issue, follow these steps:

Step 1: Check the ABI of the contract

Open your smart contract and check its ABI in the Truffle Explorer or Ganache console. This will help you identify any methods that are not in the contract’s ABI.

Step 2: Update your contract HERE

If the method is missing from the contract’s ABI, update it with the correct function name. This can be done by updating the contract code with the following changes:

• In Solidity, change function declarations to function.

• Remove all method references in storage functions or contract events.

Example update

contract MyContract {

  memory bytes myData = bytes ( 32 );

  function myFunction() public pure returns (String) {;

    вернуть "Hello, world";

  } }

} }

Step 3: Using Web3 to call methods

After updating the contract ABI, you can use Web3 to call methods from your contract using libraries such as web3.js. Here is an example:

import * as web3 from 'web3';


const web3 = new web3.Web3(ganache);

const myContract = ganache.getContractAccount('myContractAddress');

myContract.myFunction().then((result) => {

  console.log(result);

});

Step 4: Use the library to handle contract interactions

If you use React, you can use libraries such as web3-react or ethers.js to handle contract interactions. These libraries provide more convenient operation and automatically update the ABI of the contract.

Example from web3-react

import * as web3 from 'web3-react';


constant Web3 = () => {

  const web3 = new web3.Web3(window.ethereum);


  const myContract = web3.getContractAccount('myContractAddress');

  return (

    

      
{myContract.myFunction()}

    

  );

};

By following these steps and using libraries like web3-react or ethers.js, you can solve the problem of not being able to call methods from your contract in a React.js application that uses Metamask as a wallet provider.