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Web3 - Demo

A Web3 JS demo built using the Truffle framework, coupled with a Rest API and basic front-end.

Installation & Setup

The following steps will walk you through the installation of packages & setup of the project.

Clone the repository

Let's clone this repository and navigate into it.

git clone https://github.com/atherkhalil/Web3-Demo.git
cd Web3-Demo

Install Truffle framework

npm install -g truffle

This will install truffle globally on your system

Compile the smart contract & build artifacts

First we will launch the truffle environment.

truffle develop

This will launch a truffle interactive console, which will look like this truffle(develop)>.

Once inside the console, run the following commands for compiling & deploying the smart contract to the Blockchain.

compile
migrate

The migrate command takes the compiled smart contract and deploys it to the Blockchain.

Inject smart contract ABI & Address in the Rest API

Navigate to build/contracts and open Production.json

copy the ABI object, which looks like this:

[
  {
    "constant": true,
    "inputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "name": "production",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "watts",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "logTime",
        "type": "uint256"
      },
      {
        "internalType": "string",
        "name": "source",
        "type": "string"
      }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
  },
  {
    "constant": false,
    "inputs": [
      {
        "internalType": "uint256",
        "name": "watt",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "timestamp",
        "type": "uint256"
      },
      {
        "internalType": "string",
        "name": "source",
        "type": "string"
      }
    ],
    "name": "log_production",
    "outputs": [],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "constant": true,
    "inputs": [
      {
        "internalType": "uint256",
        "name": "time",
        "type": "uint256"
      }
    ],
    "name": "get_production",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "watts",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "date",
        "type": "uint256"
      },
      {
        "internalType": "string",
        "name": "source",
        "type": "string"
      }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
  }
]

Navigate to the app.js file and store the copied ABI in the abi variable.

This ABI contains the function input parameters and outputs of the fucntions defined in the smart contract.
Web3 uses this ABI as an interface to invoke the smart contract functions.

Now copy the smart contract address from the truffle console which is outputted after the migrate command is run. It will be something like this:

> contract address:    0x0BbD28754fA840e4AA253E6E530Bb8DAcfC0BF75

Paste the address in the contractAddresss variable in app.js file.

Now we're ready to use the Rest API to interact with the smart contract.

Run the Rest API

Let's go ahead and lauch the Rest API.

node app

Open http://localhost:3000 to view a simple interface to Log Production & Get Production