Using Foundry with the Avalanche C-Chain

Introduction

This guide shows how to deploy and interact with smart contracts using foundry on a local Avalanche Network and the Fuji C-Chain.

Foundry toolchain is a smart contract development toolchain written in Rust. It manages your dependencies, compiles your project, runs tests, deploys, and lets you interact with the chain from the command-line.

Recommended Knowledge

• Basic understanding of Solidity and Avalanche.
• You are familiar with Avalanche Smart Contract Quickstart.
• Basic understanding of the Avalanche's architecture
• performed a cross-chain swap via this this tutorial to get funds to your C-Chain address.

Requirements

• You have installed Foundry and run foundryup. This installation includes the forge and cast binaries used in this walk-through.
• NodeJS version 16.x

AvalancheGo and Avalanche Network Runner

AvalancheGo is an Avalanche node implementation written in Go.

Avalanche Network Runner is a tool to quickly deploy local test networks. Together, you can deploy local test networks and run tests on them.

Start a local five node Avalanche network:

cd /path/to/avalanche-network-runner
# start a five node staking network
./go run examples/local/fivenodenetwork/main.go

A five node Avalanche network is running on your machine. Network will run until you Ctrl + C to exit.

Getting Started

This section will walk you through creating an ERC721.

Clone Avalanche Smart Contract Quick Start

Clone the quickstart repository and install the necessary packages via yarn.

git clone https://github.com/ava-labs/avalanche-smart-contract-quickstart.git
cd avalanche-smart-contract-quickstart
yarn

info

The repository cloning method used is HTTPS, but SSH can be used too:

git clone [email protected]:ava-labs/avalanche-smart-contract-quickstart.git

You can find more about SSH and how to use it here.

In order to deploy contracts, you need to have some AVAX. You can get testnet AVAX from the Avalanche Faucet, which is an easy way to get to play around with Avalanche. If you already have an AVAX balance greater than zero on Mainnet, paste your C-Chain address there, and request test tokens. Otherwise, please request a faucet coupon on Guild. Admins and mods on the official Discord can provide testnet AVAX if developers are unable to obtain it from the other two options. After getting comfortable with your code, you can run it on Mainnet after making the necessary changes to your workflow.

Write Contracts

We will use our example ERC721 smart contract, NFT.sol found in ./contracts of our project.

//SPDX-License-Identifier: MIT
// contracts/ERC721.sol

pragma solidity >=0.6.2;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

contract NFT is ERC721 {
  using Counters for Counters.Counter;
  Counters.Counter private _tokenIds;

  constructor() ERC721("GameItem", "ITM") {}

  // commented out unused variable
  // function awardItem(address player, string memory tokenURI)
  function awardItem(address player)
    public
    returns (uint256)
  {
    _tokenIds.increment();

    uint256 newItemId = _tokenIds.current();
    _mint(player, newItemId);
    // _setTokenURI(newItemId, tokenURI);

    return newItemId;
  }
}

Let's examine this implementation of an NFT as a Game Item. We start by importing to contracts from our node modules. We import OpenZeppelin's open source implementation of the ERC721 standard which our NFT contract will inherit from. Our constructor takes the _name and _symbol arguments for our NFT and passes them on to the constructor of the parent ERC721 implementation. Lastly we implement the awardItem function which allows anyone to mint an NFT to a player's wallet address. This function increments the currentTokenId and makes use of the _mint function of our parent contract.

Compile, Deploy, and Verify with Forge

Forge is a command-line tool that ships with Foundry. Forge tests, builds, and deploys your smart contracts.

It requires some initial project configuration in the form of a foundry.toml which can be generated by running:

forge init --no-git --no-commit --force

The foundry.toml by default points to the folders it added. We will want to change this to make sure the src points to the contracts directory. Change your foundry.toml to look like the following:

[profile.default]
src = 'contracts'
out = 'out'
libs = ["node_modules", "lib"]
remappings = [
    '@ensdomains/=node_modules/@ensdomains/',
    '@openzeppelin/=node_modules/@openzeppelin/',
    'hardhat/=node_modules/hardhat/',
]

# See more config options https://github.com/foundry-rs/foundry/tree/master/config

To compile the NFT contract run:

forge build

By default, the contract artifacts will be in the out directory, as specified in the foundry.toml. To deploy our compiled contract with Forge we have to set environment variables for the RPC endpoint and the private key we want to use to deploy.

Set your environment variables by running:

export RPC_URL=<YOUR-RPC-ENDPOINT>
export PRIVATE_KEY=<YOUR-PRIVATE-KEY>

Since we are deploying to Fuji testnet, our RPC_URL export should be:

export RPC_URL=https://api.avax-test.network/ext/bc/C/rpc

If you would like to verify you contracts during the deployment process (fastest and easiest way), get a Snowtrace API Key. Add this as an environment variable:

export ETHERSCAN_API_KEY=<YOUR-SNOWTRACE-API-KEY>

Once set, you can deploy your NFT with Forge by running the command below while adding the values for _name and _symbol, the relevant constructor arguments of the NFT contract. You can verify the contracts with Snowtrace by adding --verify before the --constructor-args:

forge create NFT --rpc-url=$RPC_URL --private-key=$PRIVATE_KEY --verify --constructor-args GameItem ITM

Upon successful deployment, you will see the deploying wallet's address, the contract's address as well as the transaction hash printed to your terminal.

Here's an example output from an NFT deployment and verification.

[⠔] Compiling...
No files changed, compilation skipped
Deployer: 0x8db97c7cece249c2b98bdc0226cc4c2a57bf52fc
Deployed to: 0x52c84043cd9c865236f11d9fc9f56aa003c1f922
Transaction hash: 0xf35c40dbbdc9e4298698ad1cb9937195e5a5e74e557bab1970a5dfd42a32f533

Upon successful verification, after your deployment you will see the contract verification status as successfully verified:

Starting contract verification...
Waiting for etherscan to detect contract deployment...
Start verifying contract `0x8e982a4ef70430f8317b5652bd5c28f147fbf912` deployed on fuji

Submitting verification for [contracts/NFT.sol:NFT] "0x8e982a4Ef70430f8317B5652Bd5C28F147FBf912".

Submitting verification for [contracts/NFT.sol:NFT] "0x8e982a4Ef70430f8317B5652Bd5C28F147FBf912".
Submitted contract for verification:
	Response: `OK`
	GUID: `cfkyqwvjjauafirepxt8qhks2zhptczzccqege9uefu9ma8wiz`
	URL:
        https://testnet.snowtrace.io/address/0x8e982a4ef70430f8317b5652bd5c28f147fbf912
Contract verification status:
Response: `NOTOK`
Details: `Pending in queue`
Contract verification status:
Response: `OK`
Details: `Pass - Verified`
Contract successfully verified

Note: Please store your Deployed to address for use in the next sections.

Verifying After Deployment

If you did not verify within the deployment process, you can still verify a deployed contract with foundry, using forge verify-contract.

Note: The foundry.toml and environment variables will have to be set like they were in the previous section

For example, if we were to verify the NFT contract we just deployed in the previous section it would look this:

forge verify-contract --chain-id 43113 --watch --constructor-args $(cast abi-encode "constructor(string,string)" "GameItem" "ITM") 0x8e982a4ef70430f8317b5652bd5c28f147fbf912 NFT

Upon successful verification, you will see the contract verification status as successfully verified:

Starting contract verification...
Waiting for etherscan to detect contract deployment...
Start verifying contract `0x8e982a4ef70430f8317b5652bd5c28f147fbf912` deployed on fuji

Submitting verification for [contracts/NFT.sol:NFT] "0x8e982a4Ef70430f8317B5652Bd5C28F147FBf912".

Submitting verification for [contracts/NFT.sol:NFT] "0x8e982a4Ef70430f8317B5652Bd5C28F147FBf912".
Submitted contract for verification:
	Response: `OK`
	GUID: `cfkyqwvjjauafirepxt8qhks2zhptczzccqege9uefu9ma8wiz`
	URL:
        https://testnet.snowtrace.io/address/0x8e982a4ef70430f8317b5652bd5c28f147fbf912
Contract verification status:
Response: `NOTOK`
Details: `Pending in queue`
Contract verification status:
Response: `OK`
Details: `Pass - Verified`
Contract successfully verified

Using Cast to Interact with the Smart Contract

We can call functions on our NFT contract with Cast, Foundry's command-line tool for interacting with smart contracts, sending transactions, and getting chain data. In this scenario, we will mint a Game Item to a player's wallet using the awardItem function in our smart contract.

Mint an NFT from your contract by replacing <NFT-CONTRACT-ADDRESS> with your Deployed to address and <NFT-RECIPIENT-ADDRESS> with an address of your choice.

Note: This section assumes that you have already set your RPC and private key env variables during deployment

cast send --rpc-url=$RPC_URL  <NFT-CONTRACT-ADDRESS> "awardItem(address)" <NFT-RECIPIENT-ADDRESS> --private-key=$PRIVATE_KEY

Upon success, the command line will display the transaction data.

blockHash               0x1d9b0364fe002eeddd0e32be0c27d6797c63dffb51fe555ea446357759e6a6f8
blockNumber             10714448
contractAddress
cumulativeGasUsed       90837
effectiveGasPrice       28000000000
gasUsed                 90837
logs                    [{"address":"0x45857b942723fff8ee7acd2b1d6515d9965c16e5","topics":["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef","0x0000000000000000000000000000000000000000000000000000000000000000","0x000000000000000000000000845095a03a6686e24b90fed55e11f4ec808b1ab3","0x0000000000000000000000000000000000000000000000000000000000000001"],"data":"0x","blockHash":"0x1d9b0364fe002eeddd0e32be0c27d6797c63dffb51fe555ea446357759e6a6f8","blockNumber":"0xa37d50","transactionHash":"0x4651ae041a481a6eeb852e5300e9be48e66a1d2332733df22d8e75cf460b0c2c","transactionIndex":"0x0","logIndex":"0x0","removed":false}]
logsBloom               0x00000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000040000000000000000000000000008010000000000000000040000000000000000000000000000020000040000000000000800000000002000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000060080000000000000000000000000000000000000000000000000000000000000000
root
status                  1
transactionHash         0x4651ae041a481a6eeb852e5300e9be48e66a1d2332733df22d8e75cf460b0c2c
transactionIndex        0
type                    2

Well done! You just minted your first NFT from your contract. You can check the owner of tokenId 1 by running the cast call command below:

cast call --rpc-url=$RPC_URL --private-key=$PRIVATE_KEY <NFT-CONTRACT-ADDRESS> "ownerOf(uint256)" 1

The address you provided above should be returned as the owner.

0x000000000000000000000000845095a03a6686e24b90fed55e11f4ec808b1ab3

Mainnet Workflow

The Fuji workflow above can be adapted to Mainnet with the following modifications to the environment variables:

export RPC_URL=https://api.avax.network/ext/bc/C/rpc
export PRIVATE_KEY=<YOUR-PRIVATE-KEY>

Local Workflow

The Fuji workflow above can be adapted to a Local Network by doing following:

In a new terminal navigate to your Avalanche Network Runner directory.

cd /path/to/Avalanche-Network-Runner

Next, deploy a new Avalanche Network with five nodes (a Cluster) locally.

go run examples/local/fivenodenetwork/main.go

Next, modify the environment variables in your Foundry project:

export RPC_URL=http://localhost:9650/ext/bc/C/rpc
export PRIVATE_KEY=56289e99c94b6912bfc12adc093c9b51124f0dc54ac7a766b2bc5ccf558d8027

warning

The example PRIVATE_KEY variable above provides a pre-funded account on Avalanche Network Runner and should be used for LOCAL DEVELOPMENT ONLY.

Summary

Now you have the tools you need to launch a local Avalanche network, create a Foundry project, as well as create, compile, deploy and interact with Solidity contracts.

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