React Web3 Tutorial: Building a DApp with Ethereum and React Native
In today's digital age, cryptocurrencies have evolved beyond being mere speculative assets into an essential part of our financial infrastructure. With blockchain technology powering these currencies, developers are exploring new possibilities for decentralized applications (DApps) that utilize this technology to revolutionize the way we interact with data, services, and even financial transactions.
In this tutorial, we will guide you through creating a simple DApp using Ethereum smart contracts and React Native, one of the most popular frameworks for building mobile apps. By the end of this tutorial, you'll have a basic understanding of how to work with Ethereum in a React Native environment, allowing you to build your own Web3 applications or continue learning more complex features.
Setting Up Your Development Environment
To get started, ensure you have Node.js and npm installed on your system. Additionally, we will use `npm` for package management and installation within this tutorial. You'll also need a local version of Ethereum running, which can be achieved through tools like Ganache or Truffle Suite. This is necessary because Web3.js interacts directly with the Ethereum blockchain, and a local node provides that connection in development mode.
Step 1: Installing React Native and Required Packages
First, we need to install React Native on your machine. Open a terminal and run the following command:
```bash
npx react-native init MyApp
```
This command will initialize a new React Native project with a basic structure.
Next, navigate into your project directory and add necessary packages using `npm`:
```bash
cd MyApp
npm install web3 ethereumjs-util
react-native run-android # or react-native run-ios for Android/iOS respectively
```
Remember to link the native modules in your React Native build configuration:
For iOS:
```bash
pod install
```
For Android:
Add the following line to `build.gradle` inside the android folder:
```groovy
// Adds native libraries to be built and linked into our APK
externalNativeBuild {
cmake {
cppFlags "-std=c++11 -frtti -fexceptions"
abiFilters "x86;x86_64"
}
}
```
After linking, rebuild your React Native app:
```bash
react-native run-android # or react-native run-ios for Android/iOS respectively
```
Step 2: Interacting with Ethereum Smart Contracts
To interact with the Ethereum blockchain, you'll need to use `web3.js` and a smart contract deployed on your local Ganache node. For simplicity, let's create a basic smart contract that stores a username. We will deploy this contract using Remix IDE (https://remix.ethereum.org/).
First, write the Solidity code for your contract:
```solidity
pragma solidity ^0.5.16;
contract UserInfo {
mapping(address => string) public userName;
function setUserName(string memory _name) public{
userName[msg.sender] = _name;
}
function getUserName() public view returns (string){
return userName[msg.sender];
}
}
```
Deploy this contract in Remix and copy the address of your deployed contract to use it later.
Step 3: Connecting React Native App with Ethereum Network
Next, let's add a simple feature to our app that allows users to set their username on the blockchain. We will create an input field where they can enter their name and a button to execute this action on pressing.
First, import necessary modules in your JS file:
```javascript
import { Button, TextInput } from 'react-native';
const Web3 = require('web3');
// ... more imports for helper functions
```
Create an array to store users and a username variable:
```javascript
let userArray = [];
let username;
```
Now, we'll create our setUsername function that connects with Ethereum using `web3.js` and sets the username in our smart contract:
```javascript
async function setUsername(address) {
// Use this Web3 instance to connect with ethereum node
let web3 = new Web3(Web3.givenProvider || 'http://localhost:8545');
const account = await web3.eth.getAccounts();
await web3.eth.sendTransaction({from: account, to: contractAddress, data: encodeABIString('setUserName(bytes32)', [username])}, (err, result) => {});
}
```
Don't forget to include the ABI of your smart contract and connect it with `web3.js` by passing it as a parameter while creating Web3 instance. You can also parse logs emitted from your contract using `eth.getPastLogs()` or `eth.getTransactionReceipt(txHash).logs[].`
Step 4: Displaying User Information on the App
To display user's username in our app, we need a function that reads the username from Ethereum and updates it in our React Native application state. This is how you read data back from your smart contract:
```javascript
async function getUsername(address) {
let web3 = new Web3(Web3.givenProvider || 'http://localhost:8545');
const account = await web3.eth.getAccounts();
return contract.methods.getUserName().call({from: address});
}
```
Finally, integrate these functions into your app UI by calling them whenever necessary or when the user performs an action (like pressing a button) to trigger Ethereum transactions and log data.
Conclusion
This tutorial has provided you with a basic understanding of how to build a simple DApp using React Native and Ethereum smart contracts. The possibilities are almost endless; from gaming applications, voting systems, decentralized marketplaces, or even more complex features like token sales can be implemented using Ethereum's capabilities.
Remember that the world of blockchain development is vast and constantly evolving. There's always something new to learn, whether it's about smart contracts, front-end frameworks, or connecting your application with various other decentralized services. The best way to grow in this field is by practice - start building!