DISCLAIMER

Hello Starknet community, this repository is not updated with the latest Cairo syntax and hence, we do not recommend to attempt this tutorial as of today. If you are interested in contributing to the repository to update the tutorial, please create a PR and tag me @gyan0890 on it and we will be happy to support you with the process.

A great resource to get you up to speed with the new Cairo syntax in a Starknet context is Chapter 2 of the Starknet Book.

You can also ping me(@gyanlakshmi) on Telegram to help you assign the right tasks.

ERC20 on Starknet

Welcome! This is an automated workshop that will explain how to deploy an ERC20 token on Starknet and customize it to perform specific functions. The ERC20 standard is described here It is aimed at developers that:

• Understand Cairo syntax
• Understand the ERC20 token standard

This tutorial was written by Florian Charlier (@trevis_dev) in collaboration with Henri Lieutaud and Lucas Levy, based on Henri's original ERC20 101 and ERC20 102 tutorials for Solidity.

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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 Mainnnet. ​ 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 ERC20 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 ERC20 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 third 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	Starknet ERC721
Deploy and customize an ERC20 token (you are here)	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-erc20
cd starknet-erc20

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 recommand 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

Step 4 - Define your environment variables to set up your account

export STARKNET_NETWORK=alpha-goerli
export STARKNET_WALLET=starkware.starknet.wallets.open_zeppelin.OpenZeppelinAccount

Step 5 - Create and deploy your account

Before deploying your account, send a few Goerli ETH to it.

starknet new_account
starknet deploy_account

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 ex2_test_erc20 on the evaluator contract

Notes: To deploy a smart contract, follow these instructions:

starknet-compile my_contrats/erc20.cairo --output artifacts/erc20.json
starknet declare --contract artifacts/erc20.json

Use the contract class from the output of the previous command

starknet deploy --class_hash <compile_contract_class_hash> --network alpha-goerli

Your objective is to gather as many ERC20-101 points as possible. Please note :

• The 'transfer' function of ERC20-101 has been disabled to encourage you to finish the tutorial with only one address
• In order to receive points, you will have to reach the calls to the validate_and_distribute_points_once function.
• This repo contains two interfaces (IERC20Solution.cairo and IExerciseSolution.cairo). For example, for the first part, your ERC20 contract will have to conform to the first interface in order to validate the exercises; that is, your contract needs to implement all the functions described in IERC20Solution.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	0x228c0e6db14052a66901df14a9e8493c0711fa571860d9c62b6952997aae58b
Evaluator	0x14ece8a1dcdcc5a56f01a987046f2bd8ddfb56bc358da050864ae6da5f71394
Dummy ERC20 token (DTK20)	0x66aa72ce2916bbfc654fd18f9c9aaed29a4a678274639a010468a948a5e2a96

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Tasks list

Today you will deploy your own ERC20 token on Starknet!

The tutorial is structured in two parts

• In the first part (exercises 1 to 9), you will have to deploy an ERC-20 contract.
• In the second part (exercises 10 to 18), you will deploy another contract that will itself have to interact with ERC20 tokens.

Exercise 1 - Deploy an ERC20

• Call ex1_assign_rank() in the evaluator contract to receive a random ticker for your ERC20 token, as well as an initial token supply (1 pt). You can read your assigned ticker and supply through the evaluator page in voyager by calling getters read_ticker() and read_supply()
• Create an ERC20 token contract with the proper ticker and supply. You can use this implementation as a base (2 pts)
• Deploy it to the testnet (check the constructor for the needed arguments. Also note that the arguments should be decimals.) (1pt)

starknet-compile contracts/token/ERC20/ERC20.cairo --output artifacts/ERC20.json
starknet deploy --contract ERC20 --inputs arg1 arg2 arg3 --network alpha-goerli 

• Call submit_erc20_solution() in the Evaluator to set the contract you want evaluated (2pts) (Previous 3 points for the ERC20 and the deployment are also attributed at that step)

Exercise 2 - Verifying your ERC20

• Call ex2_test_erc20() in the evaluator for it to check ticker and supply and attribute your points (2 pts)

Exercise 3 - Creating a faucet

• Create a get_tokens() function in your contract. It should mint some of your token for the caller. It should return the exact amount it mints so that the Evaluator can check that the increase of balance and the amount sent corresponds.
• Deploy your contract and call submit_erc20_solution() in the Evaluator to register it
• Call the ex3_test_get_token() function that distributes tokens to the caller (2 pts).

Exercises 4, 5 and 6 - Creating an allow list

• Create a customer allow listing function. Only allow listed users should be able to call get_tokens().
• Create a function request_allowlist() that the evaluator will call during the exercise check to be allowed to get tokens.
• Create a function allowlist_level() that can be called by anyone to know whether an account is allowed to get tokens.
• Deploy your contract and call submit_erc20_solution() in the Evaluator to register it
• Call ex4_5_6_test_fencing() in the evaluator to show
  • It can't get tokens using get_tokens() (1 pt)
  • It can call request_allowlist() and have confirmation that it went through (1 pt)
  • It can then get tokens using the same get_tokens() (2 pt)

Exercises 7, 8 and 9 - Creating a multi tier allow list

• Create a customer multi tier listing function. Only allow listed users should be able to call get_token(); and customers should receive a different amount of tokens based on their level
• Create a function request_allowlist_level() that the evaluator will call during the exercise check to be allowed to get tokens at a certain tier level
• Modify the function allowlist_level() so that it returns the allowed level of accounts.
• Deploy your contract and call submit_erc20_solution() in the Evaluator to register it
• Call ex7_8_9_test_fencing_levels() in the evaluator to show
  • It can't get tokens using get_tokens() (1 pt)
  • It can call request_allowlist_level(1) , then call get_tokens() and get N tokens (2 pt)
  • It can call request_allowlist_level(2) , then call get_tokens() and get > N tokens (2 pt)

Exercise 10 - Claiming dummy tokens

• Manually claim tokens on the predeployed claimable ERC20 (DTK tokens) (1 pts)
• Claim your points by calling ex10_claimed_tokens() in the evaluator (1 pts)

Exercise 11 - Calling the faucet from your contract

• Create a contract ExerciseSolution that:
  • Can claim and hold DTK tokens on behalf of the calling address
  • Keeps track of addresses who claimed tokens, and how much
  • Implements a tokens_in_custody function to show these claimed amounts
• Deploy your contract and call submit_exercise_solution() in the Evaluator to register it
• Call ex11_claimed_from_contract() in the evaluator to prove your code works (3 pts)

Exercise 12 - Using transferFrom on an ERC20

• Create a function withdraw_all_tokens() in ExerciseSolution to withdraw the claimed tokens from the ExerciseSolution to the address that initially claimed them
• Deploy your contract and call submit_exercise_solution() in the Evaluator to register it
• Call ex12_withdraw_from_contract() in the evaluator to prove your code works (2 pts)

Exercise 13 - Approve

• Mint some DTK tokens and use voyager to authorize the evaluator to manipulate them
• Call ex13_approved_exercise_solution() to claim points (1 pts)

Exercise 14 - Revoking approval

• Use voyager to revoke the previous authorization.
• Call ex14_revoked_exercise_solution() to claim points (1 pts)

Exercise 15 - Using transferFrom

• Create a function deposit_tokens() in your contract through which a user can deposit DTKs in ExerciseSolution, by using the transferFrom of DTK
• Deploy your contract and call submit_exercise_solution() in the Evaluator to register it
• Call ex15_deposit_tokens in the evaluator to prove your code works (2 pts)

Exercise 16 and 17 - Tracking deposits with a wrapping ERC20

• Create and deploy a new ERC20 ExerciseSolutionToken to track user deposit. This ERC20 should be mintable and mint authorization given to ExerciseSolution
• Deploy ExerciseSolutionToken and make sure that ExerciseSolution knows its address
• Update the deposit function on ExerciseSolution so that user balances are tokenized: when a deposit is made in ExerciseSolution, tokens are minted in ExerciseSolutionToken and transferred to the address depositing
• Deploy your contract and call submit_exercise_solution() in the Evaluator to register it
• Call ex16_17_deposit_and_mint in the evaluator to prove your code works (4 pts)

Exercise 18 - Withdrawing tokens and burning wrapped tokens

• Update the ExerciseSolution withdraw function so that it uses transferFrom() in ExerciseSolutionToken, burns these tokens, and returns the DTKs
• Deploy your contract and call submit_exercise_solution() in the Evaluator to register it
• Call ex18_withdraw_and_burn in the evaluator to prove your code works (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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