ERC721 on StarkNet

Welcome! This is an automated workshop that will explain how to deploy an ERC721 token on StarkNet and customize it to perform specific functions. The ERC721 standard is described here. It is aimed at developers that:

• Understand Cairo syntax
• Understand the ERC721 token standard ​ ​

Introduction

Disclaimer

​ Don't expect any kind of benefit from using this, other than learning a bunch of cool stuff about StarkNet, the first general purpose validity rollup on the Ethereum Mainnet. ​ StarkNet is still in Alpha. This means that development is ongoing, and the paint is not dry everywhere. Things will get better, and in the meanwhile, we make things work with a bit of duct tape here and there! ​

How it works

The goal of this tutorial is for you to customize and deploy an ERC721 contract on StarkNet. Your progress will be check by an evaluator contract, deployed on StarkNet, which will grant you points in the form of ERC20 tokens.

Each exercise will require you to add functionality to your ERC721 token.

For each exercise, you will have to write a new version on your contract, deploy it, and submit it to the evaluator for correction.

Where am I?

This workshop is the second in a series aimed at teaching how to build on StarkNet. Checkout out the following:

Topic	GitHub repo
Learn how to read Cairo code	Cairo 101
Deploy and customize an ERC721 NFT (you are here)	StarkNet ERC721
Deploy and customize an ERC20 token	StarkNet ERC20
Build a cross layer application	StarkNet messaging bridge
Debug your Cairo contracts easily	StarkNet debug
Design your own account contract	StarkNet account abstraction

Providing feedback & getting help

Once you are done working on this tutorial, your feedback would be greatly appreciated!

Please fill out this form to let us know what we can do to make it better.

​ And if you struggle to move forward, do let us know! This workshop is meant to be as accessible as possible; we want to know if it's not the case.

​ Do you have a question? Join our Discord server, register, and join channel #tutorials-support ​ Are you interested in following online workshops about learning how to dev on StarkNet? Subscribe here

Contributing

This project can be made better and will evolve as StarkNet matures. Your contributions are welcome! Here are things that you can do to help:

• Create a branch with a translation to your language
• Correct bugs if you find some
• Add an explanation in the comments of the exercise if you feel it needs more explanation
• Add exercises showcasing your favorite Cairo feature

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Getting ready to work

Step 1 - Clone the repo

git clone https://github.com/starknet-edu/starknet-erc721
cd starknet-erc721

Step 2 - Set up your environment

There are two ways to set up your environment on StarkNet: a local installation, or using a docker container

• For Mac and Linux users, we recommend either
• For windows users we recommend docker

For a production setup instructions we wrote this article.

Option A - Set up a local python environment

• Set up the environment following these instructions
• Install OpenZeppelin's cairo contracts.

pip install openzeppelin-cairo-contracts

Option B - Use a dockerized environment

• Linux and macos

for mac m1:

alias cairo='docker run --rm -v "$PWD":"$PWD" -w "$PWD" shardlabs/cairo-cli:latest-arm'

for amd processors

alias cairo='docker run --rm -v "$PWD":"$PWD" -w "$PWD" shardlabs/cairo-cli:latest'

• Windows

docker run --rm -it -v ${pwd}:/work --workdir /work shardlabs/cairo-cli:latest

Step 3 -Test that you are able to compile the project

starknet-compile contracts/Evaluator.cairo

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Working on the tutorial

Workflow

To do this tutorial you will have to interact with the Evaluator.cairo contract. To validate an exercise you will have to

• Read the evaluator code to figure out what is expected of your contract
• Customize your contract's code
• Deploy it to StarkNet's testnet. This is done using the CLI.
• Register your exercise for correction, using the submit_exercise function on the evaluator. This is done using Voyager.
• Call the relevant function on the evaluator contract to get your exercise corrected and receive your points. This is done using Voyager.

For example to solve the first exercise the workflow would be the following:

deploy a smart contract that answers ex1 → call submit_exercise on the evaluator providing your smart contract address → call ex1_test_erc721 on the evaluator contract

Your objective is to gather as many ERC721-101 points as possible. Please note :

• The 'transfer' function of ERC721-101 has been disabled to encourage you to finish the tutorial with only one address
• In order to receive points, the evaluator has to reach the calls to the distribute_point function.
• This repo contains an interface IExerciseSolution.cairo. Your ERC721 contract will have to conform to this interface in order to validate some exercises; that is, your contract needs to implement all the functions described in IExerciseSolution.cairo.
• We really recommend that your read the Evaluator.cairo contract in order to fully understand what's expected for each exercise. A high level description of what is expected for each exercise is provided in this readme.
• The Evaluator contract sometimes needs to make payments to buy your tokens. Make sure he has enough dummy tokens to do so! If not, you should get dummy tokens from the dummy tokens contract and send them to the evaluator

Contracts code and addresses

Contract code	Contract on voyager
Points counter ERC20	0xa0b943234522049dcdbd36cf9d5e12a46be405d6b8757df2329e6536b40707
Evaluator	0x2d15a378e131b0a9dc323d0eae882bfe8ecc59de0eb206266ca236f823e0a15
Dummy ERC20 token	0x52ec5de9a76623f18e38c400f763013ff0b3ff8491431d7dc0391b3478bf1f3
Dummy ERC721 token	0x4fc25c4aca3a8126f9b386f8908ffb7518bc6fefaa5c542cd538655827f8a21

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Tasks list

Today we are creating an animal registry! Animals are bred by breeders. They can be born, die, reproduce, be sold. You will implement these features little by little.

Exercise 1 - Deploying an ERC721

• Create an ERC721 token contract. You can use this implementation as a base
• Deploy it to the testnet (check the constructor for the needed arguments. Also note that the arguments should be decimals.)

starknet-compile contracts/ERC721/ERC721.cairo --output artifacts/ERC721.json
starknet deploy --contract artifacts/ERC721.json --inputs arg1 arg2 arg3 --network alpha-goerli 

• Give token #1 to Evaluator contract
• Call submit_exercise() in the Evaluator to configure the contract you want evaluated (4 pts)
• Call ex1_test_erc721() in the evaluator to receive your points (2 pts)

Exercise 2 - Creating token attributes

• Call ex2a_get_animal_rank() to get assigned a random creature to create.
• Read the expected characteristics of your animal from the Evaluator
• Create the tools necessary to record animals characteristics in your contract and enable the evaluator contract to retrieve them trough get_animal_characteristics function on your contract (check this)
• Deploy your new contract
• Mint the animal with the desired characteristics and give it to the evaluator
• Call submit_exercise() in the Evaluator to configure the contract you want evaluated
• Call ex2b_test_declare_animal() to receive points (2 pts)

Exercise 3 - Minting NFTs

• Create a function to allow breeders to mint new animals with the specified characteristics
• Deploy your new contract
• Call submit_exercise() in the Evaluator to configure the contract you want evaluated
• Call ex3_declare_new_animal() to get points (2 pts)

Exercise 4 - Burning NFTs

• Create a function to allow breeders to declare dead animals (burn the NFT)
• Deploy your new contract
• Call submit_exercise() in the Evaluator to configure the contract you want evaluated
• Call ex4_declare_dead_animal() to get points (2 pts)

Exercise 5 - Adding permissions and payments

• Use dummy token faucet to get dummy tokens
• Use ex5a_i_have_dtk() to show you managed to use the faucet (2 pts)
• Create a function to allow breeder registration.
• This function should charge the registrant for a fee, paid in dummy tokens (check registration_price)
• Add permissions. Only allow listed breeders should be able to create animals
• Deploy your new contract
• Call submit_exercise() in the Evaluator to configure the contract you want evaluated
• Call ex5b_register_breeder() to prove your function works. If needed, send dummy tokens first to the evaluator (2pts)

Exercise 6 - Claiming an NFT

• Mint a NFT with metadata on this dummy ERC721 token , usable here
• Check it on Aspect
• Claim points on ex6_claim_metadata_token (2 pts)

Exercise 7 - Adding metadata

• Create a new ERC721 contract that supports metadata. You can use this contract as a base
• The base token URI is the chosen IPFS gateway
• You can upload your NFTs directly on this website
• Your tokens should be visible on Aspect once minted!
• Deploy your new contract
• Call submit_exercise() in the Evaluator to configure the contract you want evaluated
• Claim points on ex7_add_metadata (2 pts)

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Annex - Useful tools

Converting data to and from decimal

To convert data to felt use the utils.py script To open Python in interactive mode after running script

python -i utils.py

>>> str_to_felt('ERC20-101')
1278752977803006783537

Checking your progress & counting your points

​ Your points will get credited in your wallet; though this may take some time. If you want to monitor your points count in real time, you can also see your balance in voyager! ​

• Go to the ERC20 counter in voyager, in the "read contract" tab
• Enter your address in decimal in the "balanceOf" function

You can also check your overall progress here ​

Transaction status

​ You sent a transaction, and it is shown as "undetected" in voyager? This can mean two things: ​

• Your transaction is pending, and will be included in a block shortly. It will then be visible in voyager.
• Your transaction was invalid, and will NOT be included in a block (there is no such thing as a failed transaction in StarkNet). ​ You can (and should) check the status of your transaction with the following URL https://alpha4.starknet.io/feeder_gateway/get_transaction_receipt?transactionHash= , where you can append your transaction hash. ​

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