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Using Remix IDE for Compiling and Deploying the Smart Contracts

Lesson Objectives

By the end of this lesson, you will be able to:

Use Remix IDE for writing, compiling and deploying smart contracts on BNB Chain.
Verify deployed smart contract using Remix IDE.

Overview

In this lesson, we provide a detailed demo on how to create, compile and deploy a simple smart contract on the BNB Smart Chain Testnet using the Remix IDE. Remember that, BNB Smart Chain is the component of the BNB Chain ecosystem that is equipped with the smart contract programmability and hence any smart contract or dapps are in essence deployed on the BNB Smart Chain.

What is Remix IDE

Remix IDE is used for the entire journey of smart contract development by users at every knowledge level. It requires no setup, fosters a fast development cycle and has a rich set of plugins with intuitive GUIs. The IDE comes in 2 flavors (web app or desktop app) and as a VSCode extension.

Demo

In this lesson, we provide guidelines on how to create, compile, and deploy a simple Hello World smart contract on BSC using the Remix IDE. For this hands-on guide, readers are encourged to perform the specified tasks along for a better understanding.

Software Pre-requisites

There is no need for any local environment settings for deploying solidity smart contracts on BSC using the Remix IDE.
All you require is a browser-based Web3 wallet (e.g. Binance Wallet, MetaMask, etc.) to interact with the BSC Testnet and deployed contracts.
If you are already using MetaMask, it is recommended to create a new account for testing with Remix IDE. You can do this from the account menu, which appears when you click on the account avatar in the top right corner of MetaMask interface.

You must set up all of the following Pre-requisites to be able to deploy your solidity smart contract on BSC:

Setting Up Remix IDE

Remix is an online IDE to develop smart contracts. To be able to use it for writing smart contracts in Solidity programming language, you need to choose Solidity Compiler, make sure to choose the appropriate compiler version. We used 0.8.15 for this tutorial.

Writing the Smart Contract

Create a new file, name it HelloWorld.sol, and paste the contract code given below into it.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;
contract HelloWorld {
    function sayHelloWorld() public pure returns (string memory) {
        return "Hello World";
    }
}

The first line, pragma solidity ^0.8.15 specifies that the source code is for a Solidity version greater than 0.8.15. Pragmas are common instructions for compilers about how to treat the source code (e.g., pragma once).

A contract in the sense of Solidity is a collection of code (its functions) and data (its state) that resides at a specific address on the Ethereum blockchain. Learn more about the constructor and memory in the docs.

Compile Smart Contract

Step1: Click on the button to switch to compile page.
Step2: Select the appropriate compiler version, 0.8.15 in our case.
Step3: Enable "Auto compile" and "Optimization" from Advanced Configurations.
Step4: Select HelloWorld from the contract drop-down menu.
Step5: Click "ABI" to copy the contract ABI and save it.

Configure MetaMask and Fund Your Account

Now, We have to deploy our smart contract on BNB Smart Chain Network. For that, we have to connect to the Web3 world, this can be done by many services like Binance Wallet, MetaMask, Brave, Portis etc. We will be using MetaMask. Please follow this tutorial to setup a Metamask Account for configuring the MetaMask wallet to use with BSC.

Open Metamask and select Custom RPC from the networks dropdown
Go to setting page

Add a new network

Testnet
- RPC URLs
- ChainID: 97
- Symbol: BNB
- Block Explorer: https://testnet.bscscan.com
Mainnet
- RPC URLs
- ChainID: 56
- Symbol: BNB
- Block Explorer: https://bscscan.com

Click save to finalize the network setting
Copy the public address of your account from Metamask
Head over to Faucet and request test BNB tokens.

Deploy Smart Contract

Follow the steps given below to deploy the HelloWorld smart contract on the BNB Smart Chain Testnet.

Step1: Navigate to the Deployment Page.
Step2: Select Injected Provider in the Environment dropdown
Step3: Confirm the Connection Request on the MetaMask notification.

Step4: Once Metamask is connected to Remix, click on the "Deploy" button which would generate another metamask popup that requires transaction confirmation.

Congratulations! You have successfully deployed a simple Smart Contract on the BSC Testnet. Now you can interact with the Smart Contract. Check the deployment status here: https://testnet.bscscan.com/

Flatten and Verify the Deployed Contract on BscScan

The first and foremost step is to flatten the solidity contract into a single file to be able to get it verified on BscScan.

Flatten the Smart Contract Code

Install Truffle Flattener by running the command npm install truffle-flattener
Flatten the contract by running the command in the npx truffle-flattener HelloWorld.sol > FlatHelloWorld.sol contracts directory
Clean up the licensing information.
- The flattened contract will have the same licensing note imported from each of the files.
- Multiple licensing notes in one file break the BscScan verification, so you have to leave one licensing note for the entirety of the flattened contract.
- The easiest way to clean up is to search for the SPDX mentions in the file and remove all of them except for the very first one.

Using Flattened Code to Verify

At this point, you have your flattened and cleaned-up contract ready for the BscScan verification.

Go to BscScan Testnet.
Find your deployed contract by searching it using its address.
On the main page of BscScan, on the header click Misc > Verify Contract.
In Compiler Type, select Solidity (Single file).
In Compiler Version, select v0.8.15. This is the version this tutorial used to compile the contract.
In Open Source License Type, select MIT License (MIT).
Click Continue.
Keep the Optimization option set to No as Remix does not use optimization by default.
Paste the entirety of your flattened .sol contract in the Enter the Solidity Contract Code below field.
Click Verify and Publish.
BscScan will take a few seconds to compile your contract, verify, and publish it.

Conclusion

This lesson guided you through the basics of creating and deploying a simple smart contract using the Remix IDE and MetaMask Web Wallet. It also provides step-by-step guide on how to verify and publish your deployed smart contract. This tutorial uses testnet, however, the exact same instructions and sequence will work on the mainnet as well.

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