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Metamask

Interacting With Metamask

Interacting With MetaMask

For instructions on how to install and setup Metamask to work with Harmony blockchain please click here.

You can connect and sign transactions with Metamask using the Web3 library - which is fully compatible with the Harmony RPC API.

Do not forget that an important difference from One Wallet is that Metamsk sends transactions itself (extension side). While One Wallet only sign transaction, and then sending happens on browser side.

To use next example, you need to include the following libraries:

npm i '@metamask/detect-provider' --save
npm i web3 --save
npm i 'bn.js' --save

First step - you need to detect provider and connect to Metamask:

import detectEthereumProvider from '@metamask/detect-provider';

let ethAddress;
let isAuthorised = false;

const handleAccountsChanged = (accounts) => {
  if (accounts.length === 0) {
    console.error('Not found accounts');
  } else {
    ethAddress = accounts[0];
    
    console.log('Your address: ', ethAddress);
  }
}

export const signInMetamask = async () => {
    const provider = await detectEthereumProvider();

    // @ts-ignore
    if (provider !== window.ethereum) {
      console.error('Do you have multiple wallets installed?');
    }

    if (!provider) {
      console.error('Metamask not found');
      return;
    }

    // MetaMask events
    provider.on('accountsChanged', handleAccountsChanged);

    provider.on('disconnect', () => {
      console.log('disconnect');
      isAuthorised = false;
    });
    
    provider.on('chainIdChanged', chainId => console.log('chainIdChanged', chainId));

    provider
      .request({ method: 'eth_requestAccounts' })
      .then(async params => {
        handleAccountsChanged(params);
        isAuthorised = true;
      })
      .catch(err => {
        isAuthorised = false;
        
        if (err.code === 4001) {
          console.error('Please connect to MetaMask.');
        } else {
          console.error(err);
        }
      });
}

Next step - you can use connected provider with Web3 to sign and send transactions:

new Web3(window.web3.currentProvider) 

/* provider will use network RPC, wich was selected in MetaMask */

const accounts = await ethereum.enable();
    
/* Now any request to sign a transaction will be redirected to MetaMask */

import Web3 from 'web3';
const BN = require('bn.js');

const sendTransaction = async () => {
    const web3 = new Web3(window.ethereum);
    
    const receiverAddress = '0x430506383F1Ac31F5FdF5b49ADb77faC604657B2';
    
    const gas = 6721900;
    const gasPrice = new BN(await web3.eth.getGasPrice()).mul(new BN(1));
    
    const result = await web3.eth
      .sendTransaction({
        from: account,
        to: receiverAddress,
        value: 1 * 1e18, // 1ONE
        gasPrice,
        gas,
      })
      .on('error', console.error);

    console.log(`Send tx: ${result.transactionHash} result: `, result.status);
}

After executing this function, an interactive MetaMask window will open in which you can sign the transaction and change the gasPrice / gasLimit parameters - if it necessary.

Full code example will be here: https://github.com/harmony-one/ethhmy-bridge.frontend/blob/web3_hmy/src/pages/Examples/TransactionExample.tsx

Also you can use all Provider API from official MetaMask and Web3 docs: https://docs.metamask.io/guide/ethereum-provider.html#table-of-contents

Using Metamask with Harmony Smart Contracts

For instructions on how to install and setup Metamask to work with Harmony blockchain please click here.

Project Setup

The completed code can be found here.

For reference, the smart contract code will look as follows:

pragma solidity >=0.4.22 <0.8.0;

contract Counter {
    uint256 private count = 0;
    uint256 moneyStored = 0;

    function incrementCounter() public {
        count += 1;
    }
    function decrementCounter() public {
        count -= 1;
    }

    function addMoney() payable public {
        moneyStored += msg.value;
    }

    function getCount() public view returns (uint256) {
        return count;
    }

    function getMoneyStored() public view returns (uint256){
        return moneyStored;
    }
}

For setting up your own project just replace the code in userWallet.js in One Wallet guide with the following.

import detectEthereumProvider from "@metamask/detect-provider";

let ethAddress;
let isAuthorised = false;

const handleAccountsChanged = (accounts) => {
  if (accounts.length === 0) {
    console.error("Not found accounts");
  } else {
    ethAddress = accounts[0];

    console.log("Your address: ", ethAddress);
  }
};

export const signInMetamask = async () => {
  const provider = await detectEthereumProvider();

  // @ts-ignore
  if (provider !== window.ethereum) {
    console.error("Do you have multiple wallets installed?");
  }

  if (!provider) {
    console.error("Metamask not found");
    return;
  }

  // MetaMask events
  provider.on("accountsChanged", handleAccountsChanged);

  provider.on("disconnect", () => {
    console.log("disconnect");
    isAuthorised = false;
  });

  provider.on("chainIdChanged", (chainId) =>
    console.log("chainIdChanged", chainId)
  );

  provider
    .request({ method: "eth_requestAccounts" })
    .then(async (params) => {
      handleAccountsChanged(params);
      isAuthorised = true;
    })
    .catch((err) => {
      isAuthorised = false;

      if (err.code === 4001) {
        console.error("Please connect to MetaMask.");
      } else {
        console.error(err);
      }
    });
};

This will connect your metamask.

Making Calls

Setup your contract object. Ininit.js:

import { signInMetamask } from "./walletStore";
import Web3 from "web3";
import fs from "fs";
let but = document.getElementById("inputtButton");

let web3;
let contract;

async function setupContract() {
  let contractFile = fs.readFileSync("../build/contracts/Counter.json", {
    encoding: "UTF-8",
  });
  contractFile = JSON.parse(contractFile);
  const abi = contractFile.abi;
  const contractAddress = contractFile.networks["2"].address;
  await signInMetamask();
  web3 = new Web3(window.web3.currentProvider);

  const contractInstance = new web3.eth.Contract(abi, contractAddress);
  contract = contractInstance;
}

Making a Payable Contract Call


async function demoInteraction() {
  await setupContract();
  const accounts = await web3.eth.getAccounts();
  console.log(accounts);
  const increment = await contract.methods
    .addMoney()
    .send({ from: accounts[0], value: web3.utils.wei });
  console.log(increment);
}

Making a Read-Only Call

await setupContract();
const value = await contract.methods.getMoneyStored().call();

Congratulations

You just completed the tutorial to interact with smart contract using metamask and web3 on Harmony Network!

Add or Switch to Harmony chain on Metamask

This tutorial help developers to interact with Metamask installed on a user's device, to add (or switch to) the Harmony chain's network.

Harmony is a multi-sharded chain, currently with shard 0, 1, 2 and 3 running on Mainnet. To execute the code snippet below successfull, you can test on a device that has Metamask extension / add-on installed and visible to your app.

// Harmony's Shard ID {0..3}
const shardId = 0;

try {
  const walletAddEthereumChainRequest = await ethereum.request({
    method: 'wallet_addEthereumChain',
    params: [
      {
        chainId: '0x' + Number(1666600000 + shardId).toString(16),
        chainName: 'Harmony Mainnet Shard ' + shardId,
        nativeCurrency: { name: 'ONE', symbol: 'ONE', decimals: 18 },
        rpcUrls: ['https://' + (shardId === 0 ? 'api.harmony.one' : 'api.s' + shardId + '.t.hmny.io')],
        blockExplorerUrls: ['https://explorer.harmony.one/'],
      },
    ],
  });
} catch (error) {
  console.error(error);
}

Please note that window.web3 has been deprecated. Use window.ethereum instead. To migrate, use this guide from Metamask.

When this code snippet is executed, users will see message to approve adding or switching to correct Harmony chain.

You can see more information about Metamask documentation related to the Ethereum Provider API at https://docs.metamask.io/guide/ethereum-provider.html

To see a full list of Chain IDs, please visit https://chainlist.org/ and search for Harmony

Interacting With Metamask

Interacting With MetaMask

For instructions on how to install and setup Metamask to work with Harmony blockchain please click here.

You can connect and sign transactions with Metamask using the Web3 library - which is fully compatible with the Harmony RPC API.

To use next example, you need to include the following libraries:

npm i '@metamask/detect-provider' --save
npm i web3 --save
npm i 'bn.js' --save

First step - you need to detect provider and connect to Metamask:

import detectEthereumProvider from '@metamask/detect-provider';

let ethAddress;
let isAuthorised = false;

const handleAccountsChanged = (accounts) => {
  if (accounts.length === 0) {
    console.error('Not found accounts');
  } else {
    ethAddress = accounts[0];
    
    console.log('Your address: ', ethAddress);
  }
}

export const signInMetamask = async () => {
    const provider = await detectEthereumProvider();

    // @ts-ignore
    if (provider !== window.ethereum) {
      console.error('Do you have multiple wallets installed?');
    }

    if (!provider) {
      console.error('Metamask not found');
      return;
    }

    // MetaMask events
    provider.on('accountsChanged', handleAccountsChanged);

    provider.on('disconnect', () => {
      console.log('disconnect');
      isAuthorised = false;
    });
    
    provider.on('chainIdChanged', chainId => console.log('chainIdChanged', chainId));

    provider
      .request({ method: 'eth_requestAccounts' })
      .then(async params => {
        handleAccountsChanged(params);
        isAuthorised = true;
      })
      .catch(err => {
        isAuthorised = false;
        
        if (err.code === 4001) {
          console.error('Please connect to MetaMask.');
        } else {
          console.error(err);
        }
      });
}

Next step - you can use connected provider with Web3 to sign and send transactions:

new Web3(window.web3.currentProvider) 

/* provider will use network RPC, wich was selected in MetaMask */

const accounts = await ethereum.enable();
    
/* Now any request to sign a transaction will be redirected to MetaMask */

import Web3 from 'web3';
const BN = require('bn.js');

const sendTransaction = async () => {
    const web3 = new Web3(window.ethereum);
    
    const receiverAddress = '0x430506383F1Ac31F5FdF5b49ADb77faC604657B2';
    
    const gas = 6721900;
    const gasPrice = new BN(await web3.eth.getGasPrice()).mul(new BN(1));
    
    const result = await web3.eth
      .sendTransaction({
        from: account,
        to: receiverAddress,
        value: 1 * 1e18, // 1ONE
        gasPrice,
        gas,
      })
      .on('error', console.error);

    console.log(`Send tx: ${result.transactionHash} result: `, result.status);
}

After executing this function, an interactive MetaMask window will open in which you can sign the transaction and change the gasPrice / gasLimit parameters - if it necessary.

Full code example will be here: https://github.com/harmony-one/ethhmy-bridge.frontend/blob/web3_hmy/src/pages/Examples/TransactionExample.tsx

Also you can use all Provider API from official MetaMask and Web3 docs: https://docs.metamask.io/guide/ethereum-provider.html#table-of-contents

Using Metamask with Harmony Smart Contracts

For instructions on how to install and setup Metamask to work with Harmony blockchain please click here.

Project Setup

The completed code can be found here.

For reference, the smart contract code will look as follows:

pragma solidity >=0.4.22 <0.8.0;

contract Counter {
    uint256 private count = 0;
    uint256 moneyStored = 0;

    function incrementCounter() public {
        count += 1;
    }
    function decrementCounter() public {
        count -= 1;
    }

    function addMoney() payable public {
        moneyStored += msg.value;
    }

    function getCount() public view returns (uint256) {
        return count;
    }

    function getMoneyStored() public view returns (uint256){
        return moneyStored;
    }
}

For setting up your own project just replace the code in userWallet.js in One Wallet guide with the following.

import detectEthereumProvider from "@metamask/detect-provider";

let ethAddress;
let isAuthorised = false;

const handleAccountsChanged = (accounts) => {
  if (accounts.length === 0) {
    console.error("Not found accounts");
  } else {
    ethAddress = accounts[0];

    console.log("Your address: ", ethAddress);
  }
};

export const signInMetamask = async () => {
  const provider = await detectEthereumProvider();

  // @ts-ignore
  if (provider !== window.ethereum) {
    console.error("Do you have multiple wallets installed?");
  }

  if (!provider) {
    console.error("Metamask not found");
    return;
  }

  // MetaMask events
  provider.on("accountsChanged", handleAccountsChanged);

  provider.on("disconnect", () => {
    console.log("disconnect");
    isAuthorised = false;
  });

  provider.on("chainIdChanged", (chainId) =>
    console.log("chainIdChanged", chainId)
  );

  provider
    .request({ method: "eth_requestAccounts" })
    .then(async (params) => {
      handleAccountsChanged(params);
      isAuthorised = true;
    })
    .catch((err) => {
      isAuthorised = false;

      if (err.code === 4001) {
        console.error("Please connect to MetaMask.");
      } else {
        console.error(err);
      }
    });
};

This will connect your metamask.

Making Calls

Setup your contract object. Ininit.js:

import { signInMetamask } from "./walletStore";
import Web3 from "web3";
import fs from "fs";
let but = document.getElementById("inputtButton");

let web3;
let contract;

async function setupContract() {
  let contractFile = fs.readFileSync("../build/contracts/Counter.json", {
    encoding: "UTF-8",
  });
  contractFile = JSON.parse(contractFile);
  const abi = contractFile.abi;
  const contractAddress = contractFile.networks["2"].address;
  await signInMetamask();
  web3 = new Web3(window.web3.currentProvider);

  const contractInstance = new web3.eth.Contract(abi, contractAddress);
  contract = contractInstance;
}

Making a Payable Contract Call


async function demoInteraction() {
  await setupContract();
  const accounts = await web3.eth.getAccounts();
  console.log(accounts);
  const increment = await contract.methods
    .addMoney()
    .send({ from: accounts[0], value: web3.utils.wei });
  console.log(increment);
}

Making a Read-Only Call

await setupContract();
const value = await contract.methods.getMoneyStored().call();

Congratulations

You just completed the tutorial to interact with smart contract using metamask and web3 on Harmony Network!