Introduction to Smart Contracts

Intro-to-Smart-Contracts

//Smart Contracts are a series of Ethereum Virtual Machine OP Codes
//Solidity it higher level and is compiled to EVM bytecode

// package.json
{
  "dependencies": {
    "web3": "0.17.0-alpha",
    "solc": "^0.4.4"
  }
}

//install dependencies
npm install

//Add requirements and add new web3 instance
var Web3 = require("web3")
var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"))
var solc = require("solc")

//Make new .sol file for smart contract Introduction.sol
contract Introduction {
  
  function displayMessage() constant returns (string) {
    return "Congrats on your first smart contract";
  }
}

//Compile into bytecode in node console
var source = `[[contract syntax]]`
var compiled = solc.compile(source)

//Query contract
compiled.contracts.Introduction

//View bytecode
compiled.contracts.Introduction.bytecode

//View opcodes
compiled.contracts.Introduction.opcodes

//View ABI (public facing interface to show what methods are available to call)
compiled.contracts.Introduction.interface

//Set ABI variable
var abi = JSON.parse(compiled.contracts.Introduction.interface)

//Make contract object that is deployed to testrpc
var IntroductionContract = web3.eth.contract(abi)

//Make deployed variable
var deployed = IntroductionContract.new({
  from: web3.eth.accounts[0],
  data: compiled.contracts.Introduction.bytecode,
  gas: 4700000,
  gasPrice: 5,
}, (error, contract) => { })

//You can see in testrpc that it goes through; contract + tx address will be posted
web3.eth.getTransacton("[[transaction id]]")

//View contract address
deployed.address

//Call function on contract
deployed.displayMessage.call()