Blockchain example with reactjs , ganache , truffle , smartcontract example for beginners

1. Create a project folder with project name

2. inside the project folder first initialize truffle

   truffle init
   

3. Then initialize react in the same directory

   npx create-react-app client  
   

4. install react web3

   npm install web3
   

5. write program in react js .

6. Now start ganache

• Go to the truffle directory
• Open truffle-config.js and uncomment these lines and change port

   contracts_build_directory: "./src/abi",

   development: {
    host: "127.0.0.1",     // Localhost (default: none)
    port: 7545,            // Standard Ethereum port (default: none)
    network_id: "*",       // Any network (default: none)
   },

• type the command :

   truffle compile
  
   truffle migtate --reset
  

This will compile and deploy our smart contract

• After compiling there will be a folder called 'build' in the truffle directory
• Open that , There will be a file called 'Migration.js' .

To Create our own smart contract :

To create and deploy our own smart contract we need to create a .sol file in the folder contractes . Here we create a file Test_migrations.sol and we paste the below code

  pragma solidity >=0.4.22 <0.9.0;

  contract Test_contract 
  {
    address public owner = msg.sender;

    function testFunction () public pure returns(string memory ){
        return "hello from first test";
    }
  }

To deploy the contract create a migraion file in the migrations folder There will be one present there named '1_initial_migration' It is already defined

To deploy our contact we need to create one file with a name that you want Here we create : '2_test_migration.js' inside that file we write codes to migration

  const Test_contract = artifacts.require("Test_contract");
  // Test_contract is the name of the contract saved inside contracts folder
  module.exports = function (deployer) {
    deployer.deploy(Test_contract);
  };

then type the commands

    truffle compile

    truffle migtate --reset

If it migrate successfully there will be a file called Test_contract.json inside 'src/abi' folder

Connect metamask from chrome to ganache local network

• Click on custom rcp

• enter the host address name and etc..

• chain id will be 1337 default for localhost

• now click on the round symbol in metamask

• click on import account

• Open ganache , tap on the key symbol of the address that you wanna use , It will show a private key , copy and paste that private key to metamask

Connecting metamask with React :

8. Write react functions to connect to the metamask account

import web3 first .

The below code is the base functions to get balance , connect to wallet and etc..

const web3 = new Web3(Web3.givenProvider || "http://localhost:7545");

async function LoadBlockChain()
  {
    
    // connects to the local evelopment environment



    const ConnectToMetaMask = async () => {
      
      // This function is used to check if metamask is connected or not 

      if (window.ethereum) 
      {
        // the function enters here if metamask is installed
        console.log("metamask is present ")
        await window.ethereum.send('eth_requestAccounts');
        window.web3 = new Web3(window.ethereum);

        // console.log(window.web3);
        const acc = await web3.eth.getAccounts();

        console.log(acc)
        // The address is then stored 
        setAddress(acc)

        // In this case, the await window.ethereum.send('eth_requestAccounts') function calls the pop-up UI dialogue that asks the user’s permission to connect the dApp to MetaMask.

        setIsConnectedToWallet(true);
        // if we connect to the wallet successfully we set isConnectedToWallet to true


        // This function returns true if metamask is installed
        return true;
      }
      else{
        // the function enters here if metamask is not installed
        console.log("metamask is not installed")
      }

      // This function returns false if metamask is not installed

      return false;
    }

   await  ConnectToMetaMask()

  }






  const getBalance = async () => {
    
    if(!isConnectedToWallet)
    {
      // If wallet is not connected we enter here 
      console.log("Please connect to wallet ");
      return;
    }

    console.log("address : " , address);
    

    // prints the balance of the connected address
    const balanceFrom = web3.utils.fromWei(
       await web3.eth.getBalance( address[0] ),
       'ether'
    );

    console.log("balance is :" ,  balanceFrom )
    
 };

Connect to our smart contract .

To connect to our own smart contract we need to import the 'src/abi/Test_contract.json'; to our code which contains the informations to the connection , such as block addres ..

So first we import the file to our App.js import Test_contract from '../abi/Test_contract.json';

To connect to the smart contract we need to use the below syntax

  new web3.eth.Contract(abi , address)

here abi is Test_contract.abi and address can be found from the 'src/abi/Test_contract.json'; file . Go to that file and search for address , copy that address and paste it in the address field .

We wrtite a function to do this all and it looks like below

  const ConnectSmartContract = async () =>{
    // This function is used to connect to the smart contract 
    if(!isConnectedToWallet)
    {
      // If wallet is not connected we enter here 
      console.log("Please connect to wallet ");
      return;
    }


    // These below lines are used to fetch the address of our smart contract
    // The address is present inside the test_contract.json 

    const networkId = await web3.eth.net.getId()
    console.log( "networkId :  " , networkId );
    const networkData = Test_contract.networks[networkId];
    console.log( "network Data :  " , networkData);

    if(networkData)
    {
      var smartContractAddress = networkData.address;
      console.log( "network address :  " , smartContractAddress);
      
      // the below line is used to connect to the Test_contract , 
      // ie , our smart contract
      const TestContract =  new web3.eth.Contract( Test_contract.abi , smartContractAddress );

      console.log(TestContract);

      return TestContract;
    }
    else{
      console.log("not found");
    }

  

  }

  const smartContractFunctionCall = async () =>{
    // This function is used to call the functions in the smart contract 
    const TestContract = await ConnectSmartContract();
    // above line connect to the smart contract
    //  ConnectSmartContract() is a function we have written to connect with our smart contract 


    const dataBack = await TestContract.methods.testFunction().call();

    // This runs the TestContract and stores the return value to dataBack variable 
    

    console.log("dataBack : " , dataBack );


  }

On the console we can see

 dataBack :  hello from first test

Which is the data returned from the smart contract