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Step 4 - Integrate Blended Contracts

Step 4: Integrate Blended Contracts​

This guide is based off of the template blended application in this Github repo.

Once a blended application is deployed, you can use popular libraries such as ethers.js to integrate your application into user interfaces such as a frontend website.

🔍 Rust x Ethereum Maxi?

If you prefer Rust development, consider using alloy-rs instead of ethers.js for a more native Rust experience when interacting with blended contracts.

4.1 Add ethers.js to the Foundry project​

Add ethers.js as a dependency to your Foundry project. Note that you'll first have to initialize a npm package (as this is not by default available in Foundry nor gblend projects).

mkdir js-client && cd js-client && \
npm init -y && \
npm i ethers@5.7.2 && \
touch rust.js solidity.js && \
cd ..

4.2 Test ethers.js script to call Solidity contract​

Add the following script to the js-client/solidity.js file that was created in the step above. This script calls the FluentEvmRustTypes.sol contract, which then externally calls the Rust contract functions.

Note: update string variable contractAddress with your deployed FluentEvmRustTypes contract address.

const ethers = require("ethers") // npm i ethers@5.7.2 https://github.com/smartcontractkit/full-blockchain-solidity-course-js/discussions/5139#discussioncomment-5444517

const rpcURL = "https://rpc.testnet.fluent.xyz/" // Your RPC URL goes here

const provider = new ethers.providers.JsonRpcProvider(rpcURL)

const contractAddress = "<INPUT_SOLIDITY_CONTRACT_ADDRESS_HERE>"
const contractABI = [{"inputs":[{"internalType":"address","name":"FluentRustAddress","type":"address"}],"stateMutability":"nonpayable","type":"constructor"},{"inputs":[],"name":"rustTypesTest","outputs":[{"internalType":"contractIRustTypesTest","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustAddress","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustBool","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustBytes","outputs":[{"internalType":"bytes","name":"","type":"bytes"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustBytes32","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustInt256","outputs":[{"internalType":"int256","name":"","type":"int256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustString","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"getRustUint256","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"}]

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

let fluent_sepolia_chain_id = 20994;

testSolidityContractRead()

async function testSolidityContractRead() {

  const connectedNetworkObject = await provider.getNetwork();
  const chainIdConnected = connectedNetworkObject.chainId;
  console.log("chainIdConnected: " + chainIdConnected)

  if(chainIdConnected != fluent_sepolia_chain_id){
    console.log("RPC endpoint not connected to Fluent Sepolia (chainId: " + fluent_sepolia_chain_id + ").");
    console.log("Switch to Fluent Sepolia then try again.");
    return;
  }

  const rustTypesTestContractAddress = await contractDeployed.rustTypesTest()
  console.log("rustTypesTestContractAddress: " + rustTypesTestContractAddress)

  const rustString = await contractDeployed.getRustString()
  console.log("rustString: " + rustString)

  const rustUint256 = await contractDeployed.getRustUint256()
  console.log("rustUint256: " + rustUint256)

  const rustInt256 = await contractDeployed.getRustInt256()
  console.log("rustInt256: " + rustInt256)

  const rustAddress = await contractDeployed.getRustAddress()
  console.log("rustAddress: " + rustAddress)

  const rustBytes = await contractDeployed.getRustBytes()
  console.log("rustBytes: " + rustBytes)

  const rustBytes32 = await contractDeployed.getRustBytes32()
  console.log("rustBytes32: " + rustBytes32)

  const rustBool = await contractDeployed.getRustBool()
  console.log("rustBool: " + rustBool)

}

This script should return the expected values the Solidity contract gets from the Rust contract.

# From project root:
node js-client/solidity.js

4.3 Test ethers.js script to call Rust contract​

Add the following script to the js-client/rust.js file that was created in the step above. This script calls the Rust contract directly with the IRustEvmTypes Solidity interface.

Note: update string variable contractAddress with your deployed Rust contract address

const ethers = require("ethers") // npm i ethers@5.7.2 https://github.com/smartcontractkit/full-blockchain-solidity-course-js/discussions/5139#discussioncomment-5444517

const rpcURL = "https://rpc.testnet.fluent.xyz/" // Your RPC URL goes here

const provider = new ethers.providers.JsonRpcProvider(rpcURL)

const contractAddress = "<INPUT_RUST_CONTRACT_ADDRESS_HERE>"
const contractABI = [{"inputs":[],"name":"rustAddress","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"rustBool","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"rustBytes","outputs":[{"internalType":"bytes","name":"","type":"bytes"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"rustBytes32","outputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"rustInt256","outputs":[{"internalType":"int256","name":"","type":"int256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"rustString","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"rustUint256","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"}]

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

let fluent_sepolia_chain_id = 20994;

testRustContractRead()

async function testRustContractRead() {

  const connectedNetworkObject = await provider.getNetwork();
  const chainIdConnected = connectedNetworkObject.chainId;
  console.log("chainIdConnected: " + chainIdConnected)

  if(chainIdConnected != fluent_sepolia_chain_id){
    console.log("RPC endpoint not connected to Fluent Sepolia (chainId: " + fluent_sepolia_chain_id + ").");
    console.log("Switch to Fluent Sepolia then try again.");
    return;
  }

  const rustString = await contractDeployed.rustString()
  console.log("rustString: " + rustString)

  const rustUint256 = await contractDeployed.rustUint256()
  console.log("rustUint256: " + rustUint256)

  const rustInt256 = await contractDeployed.rustInt256()
  console.log("rustInt256: " + rustInt256)

  const rustAddress = await contractDeployed.rustAddress()
  console.log("rustAddress: " + rustAddress)

  const rustBytes = await contractDeployed.rustBytes()
  console.log("rustBytes: " + rustBytes)

  const rustBytes32 = await contractDeployed.rustBytes32()
  console.log("rustBytes32: " + rustBytes32)

  const rustBool = await contractDeployed.rustBool()
  console.log("rustBool: " + rustBool)

}

This script should return the expected values directly from the Rust contract.

# From project root:
node js-client/rust.js

🎉 Congratulations!​

You've successfully built and deployed your first blended application to Fluent Testnet! 🚀

🎨Summary

✅ Rust Contract Development - Created a Rust/WASM contract with multiple data types
✅ Solidity Contract Integration - Built a Solidity contract that seamlessly calls your Rust contract
✅ Blended Deployment - Deployed both contracts to Fluent Testnet using gblend
✅ Frontend Integration - Connected your contracts to a JavaScript frontend using ethers.js
✅ Cross-Contract Communication - Demonstrated Solidity calling Rust functions with different data types

Next Steps:​

Now that you have a working blended application, you can:

  • Explore Advanced Features - Try more complex data structures and contract interactions
  • Build User Interfaces - Create web apps, mobile apps, or CLI tools
  • Join the Community - Share your projects and get help from other developers

Thank you for being part of the Era of Expressivity! 🌟