Using Remix

Remix is an open-source, web-based development environment tailored for EVM decentralized finance (DeFi) contract development. It offers developers a comprehensive suite of tools to write, deploy, and test DeFi contracts in Solidity. For more information, visit Remix.

Add the Flow network to MetaMask

Navigate to the Using EVM page to find the button to add the Flow network information to your metamask.

Fund Your Flow Account

Navigate to the Flow Testnet Faucet to obtain FLOW tokens necessary to deploy a smart contract.

Deploy a DeFi contract with Remix

HelloWorld DeFi Contract

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// SPDX-License-Identifier: MIT

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pragma solidity ^0.8.0;

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contract HelloWorld {

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// Declare a public field of type string.

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string public greeting;

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// Constructor to initialize the greeting.

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// In Solidity, the constructor is defined with the "constructor" keyword.

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constructor() {

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greeting = "Hello, World!";

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}

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// Public function to change the greeting.

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// The "public" keyword makes the function accessible from outside the contract.

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function changeGreeting(string memory newGreeting) public {

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greeting = newGreeting;

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}

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// Public function that returns the greeting.

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// In Solidity, explicit return types are declared.

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function hello() public view returns (string memory) {

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return greeting;

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}

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}

Steps to deploy the HelloWorld DeFi contract

1. Create a file named HelloWorld.sol.
2. Select Solidity Compiler and compile HelloWorld.sol.
3. Select Deploy & Run Transactions.
4. Make sure to select Injected Provider - Metamask in Environment dropdown.
5. Deploy the HelloWorld DeFi contract.

Calling the Deployed Smart Contract

Using Ethers.js to Call the HelloWorld Smart Contract

1. Create a new get-greeting.js file under scripts.
2. Paste in the JavaScript code below.
3. Click on green play button to run.
4. Verify the greeting is "Hello World!".

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// Import ethers from the ethers.js library

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const { ethers } = require('ethers');

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// Define the contract ABI

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const contractABI = ['function hello() public view returns (string memory)'];

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// Define the contract address

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const contractAddress = '0x8a120383e6057b1f3aef4fa9b89c2f1b0a695926';

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// Connect to the Ethereum network

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// This example uses the default provider from ethers.js, which connects to the Ethereum mainnet.

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// For a testnet or custom RPC, use ethers.getDefaultProvider('networkName') or new ethers.providers.JsonRpcProvider(url)

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const provider = new ethers.providers.Web3Provider(window?.ethereum);

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// Create a new contract instance

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const contract = new ethers.Contract(contractAddress, contractABI, provider);

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// Call the hello function of the contract

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async function getGreeting() {

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const greeting = await contract.hello();

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console.log(greeting);

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}

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// Execute the function

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getGreeting();

Follow the steps below to change the greeting and retrieve the new greeting.

Updating the deployed DeFi contract

1. Select the HelloWorld.sol file.
2. Select the Deploy and Run Transaction page.
3. Make sure to select Injected Provider - Metamask in Environment dropdown.
4. Type a new greeting in the text input next to changeGreeting.
5. Click changeGreeting.
6. Sign the Metamask transaction.
7. To verify the greeting changed, re-run the get-greeting.js script above.