Setting up an Ethereum Development Environment – Compound

The MetaMask browser extension automatically imports the Web3 object as global JavaScript variable on every webpage the user visits. It uses the HTTP provider in which is selected in the pictured drop down menu(more on providers later).

Before you deploy a smart contract to an Ethereum network (or your localhost), you must first compile it to bytecode. This turns your program into machine-readable opcodes that Ethereum nodes understand how to execute.

In addition to bytecode, the Solidity compiler also produces an ABI (application binary interface). This is a JSON object that maps to your bytecode. Web3.js (and other frameworks) can do JSON RPC using the ABI, and the address of your smart contract. Think of the ABI as the bridge between Web2 and Web3.

Installing solc can be done using Homebrew on Mac or apt-get and the like on Linux distributions. Windows users need to build from source. Solidity compiler installation instructions for any OS can be found in the Solidity documentation.

Once you have installed the Solidity compiler, you can use it on the command line to compile a Solidity file. If compilation succeeds, you’ll get bytecode and a JSON ABI.

solc MySmartContracts.sol

Web3.js is a popular library for interfacing with the Ethereum blockchain. To use it in a web page, you can import the library directly using a CDN like JSDeliver.

<script src="https://cdn.jsdelivr.net/npm/web3@latest/dist/web3.min.js"></script>

To install the library for your built, front-end web project, or for a Node.js script/ server application, you can use NPM or Yarn for Node.js. Click here to install the LTS of Node.js and NPM.

npm install web3## oryarn add web3

To import Web3.js into a Node.js script or Browserify front-end project, you can use the following line of JavaScript:

const Web3 = require('web3');

If you imported via CDN directly to a web page, the `Web3` variable will already be declared; no need for the line of code above.

To initialize your Web3 object, you need to provide a network WebSocket or HTTP provider in which to point Web3. This is the default HTTP provider address and port for Ganache CLI, which you can run on your local machine.

const web3 = new Web3('http://localhost:8545');

If you want to connect to a public network via Infura, you can do so once you create an Infura account and get your API key.

const web3 = new Web3('https://mainnet.infura.io/v3/_YOUR_API_KEY_'); // Infura can also access public test nets 
// by changing the subdomain.
// Eg: https://ropsten.infura.io/v3/_YOUR_API_KEY_

Unless you already have your own Ethereum network nodes to be your entrypoint to the Ethereum network, you’ll need to make an account with a service like Infura. You get up to 100,000 API calls per day, for free, if you make a developer account at https://infura.io/.

Create a project, and copy your “Endpoint.” This contains your personal API key. Remember that you can change the subdomain of the URL to any of the public networks to switch the network your code interfaces with.

Ganache CLI, made by the Truffle team, is an essential tool for Ethereum development and testing. You can easily spin-up your own instance of Ethereum on your local machine with 1 terminal command. When you boot up Ganache, it gives you 10 Ethereum wallets that each contain 100 fake ETH. You can use this test net ETH to test smart contracts on your localhost blockchain.

ganache-cli

In addition to a blank-slate blockchain, you can also fork an existing public network. You would want to do a fork of a public net if you want to test out existing, public smart contracts on your local machine.

For example, if you want to test out supplying Ethereum assets to Compound’s Main network smart contracts, you can run Ganache with a fork of Main net. You can use the same addresses as the production Compound Protocol contracts, except interacting with them will only change the blockchain running on your local machine. Easy, streamlined development and testing.

ganache-cli -f https://mainnet.infura.io/v3/_YOUR_API_KEY_

Installing Ganache CLI can be done with NPM or Yarn. If you haven’t already click here to install the LTS of Node.js and NPM.

## Installs Ganache CLI globally so you can run it
## anywhere with `ganache-cli`npm install -g ganache-cli## or: yarn global add ganache-cli

Now that we have an understanding of basic Ethereum concepts, and we’ve set up our dev environment, we can write a full DApp. Total development time: 5 minutes.

We’re not going to use the Compound Protocol just yet. Baby steps. After you complete this walkthrough, you’ll be ready to learn how to Supply Assets to the Compound Protocol, which is the next quick start guide.

Create a directory on your local machine for your DApp project files. You can do this on the command line.

mkdir first-ethereum-dappcd first-ethereum-dapp/

We’ll write our smart contract in a Solidity file called FirstContract.sol.

touch FirstContract.sol## or on non-bash Windows CLI: fsutil file createnew FirstContract.sol 0

Open the Solidity file with your favorite text editor for writing code. I’ll be using Sublime text, which has a community-made syntax highlighter for Solidity.

Here is the code for our contract file.

solc --bin --abi -o ./build FirstContract.sol

npm init -y## OR if you're a yarn person## yarn init -y

npm install web3 ganache-cli http-server## alternatively
## yarn add web3 ganache-cli http-server

npm install -g npx## or: yarn global add npx

cd first-ethereum-dapp/npx ganache-cli

touch deploy.js

node deploy.js

> FirstContract was successfully deployed!
> FirstContract can be interfaced with at this address:
> 0x702f935d608Aadf90323310c489B2903af20AA43

touch index.html

npx http-server> Starting up http-server, serving ./
> Available on:
> http://127.0.0.1:8080
> http://192.168.1.165:8080
> Hit CTRL-C to stop the server