#HOW_TO_CRYPTO with HARDHAT!

• go from zero to crypto, in this OPENZEPPELIN walkthrough, and STUDY of Smart Contract Development Best Practices.
• derived from https://docs.openzeppelin.com/learn/
• and https://wizard.openzeppelin.com
• also HARDHAT: https://hardhat.org/getting-started/ INDEX:
• STARTUP of existing CRYPTO-PROJECT,
• CRYPTO-PROJECT, scaffold from scratch,
• ERC721 Standard.
• ADVANCED ASSERTIONS

---

STARTUP:

• compile, ganache, migrate, exec, test,

npm install npx hardhat compile npx hardhat node npx hardhat test

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1) Build a SCAFFOLD:

mkdir PROJECTS/CRYPTO/EXAMPLE && cd PROJECTS/CRYPTO/EXAMPLE npm init -y code . create README.md create ./scripts npm install --save-dev hardhat npx hardhat //creates config npx hardhat compile npx hardhat node //Hardhat Network, similar to ganache npx hardhat run scripts/sample-script.js --network localhost

• expose JSON-RPC interface.

• Connect wallet or app to http://localhost:8545. ###HARDHAT

• Hardhat Network, uses @ethereumjs/vm

• Hardhat Runner, extensible TASK RUNNER

• tasks and plugins, tasks call tasks.

• Hardhat uses /scripts to DEPLOY

npm install --save-dev @nomiclabs/hardhat-ethers ethers RESULT: crypto project ready to rock, with /contracts, /scripts, /migrations, and /test. git init GitHub with LICENSE MIT git remote paste.git git push, git pull. create s3cr3tz.json .gitignore s3cr3tz.json

---

2) SOLIDITY PROJECT!

npm install --save-dev truffle

• Truffle or Hardhat.
• Truffle uses Web3.js. Hardhat uses ethers.js
• Platforms for compile and migrate
• (to various TEST NETS)
• Like Ganache (local) or Rinkeby, public.

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3) CONTRACTS!!

create /contracts/BASIC_721_oz.sol

• go to Open Zeppelin Wizard to get code.
• compile SOL into BYTECODE for EVM
• configure truffle-config to use solc compiler.
• will compile all contracts into
• /build/contracts/artifacts

.gitignore artifacts cache

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##HARDHAT NETWORK CONSOLE

npx hardhat console --network localhost const Box = await ethers.getContractFactory('Box'); const box = await Box.attach('0x5FbDB2315678afecb367f032d93F642f64180aa3') ##HARDHAT by SCRIPT npx hardhat run --network localhost ./scripts/index.js const address = '0x5FbDB2315678afecb367f032d93F642f64180aa3'; const Box = await ethers.getContractFactory('Box'); const box = await Box.attach(address); //get address from DEPLOY ##HARDHAT UNIT TESTS npm install --save-dev chai npx hardhat test npm install --save-dev @openzeppelin/test-helpers

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4) ERC20, ERC721, ERC1155

OpenZeppelin Contract Wizard https://wizard.openzeppelin.com/ MAX ANNOTATED EXAMPLES in /contracts

npm install --save-dev @openzeppelin/contracts npx truffle compile

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5) DEVNET (testnet local)

• with Ganache-CLI

npm install --save-dev ganache-cli

• DEPLOY / migrate
• DEV by CONSOLE
• TEST RUN by scripts
• No METAMASK
• GR8 for UNIT-TESTS (next)
• RUN GANACHE

npx ganache-cli --deterministic

• configure connection with ganache (geth,parity)

create // migrations/2_deploy.js

• and configure truffle-config

networks:development:host:127.0.0.1:8545:*

• standard ETH PORT 8545
• DEPLOY contracts to DEVELOPMENT NETWORK, on GANACHE:8545

npx truffle migrate --network development

• puts BYTECODE artifacts and ABI to ganache
• if ERROR, update migrate, or restart GANACHE

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6) PROTOTYPE-TEST (local network - truffle CONSOLE)

npx truffle console --network development

• now INIT CONTRACT VARIABLE (charged 0.008 ETH)

accounts const BASIC_oz = await BASIC_oz.deployed();

• CALL TRANSACTION

await BASIC_oz.store(42)

• GET a RECEIPT BACK (charged 43755)

(await BASIC_oz.retrieve()).toString() //42

• no receipt, no transaction.
• CMD-LINE-QUERY

---

7) SCRIPT-DEV ( /script/js with Web3.js)

• Truffle executes ./scripts
• once deployed, any library sees contract
• in scripts-index: // const accounts = await web3.eth.getAccounts(); // console.log(accounts)

npx truffle exec --network development ./scripts/index.js

---

8) JS instance of CONTRACT ( Web3.js)

• Truffle CONTRACT, as JSON. // const BASIC_oz = artifacts.require('BASIC_oz'); // const _basic_oz = await BASIC_oz.deployed();
• CALL THE CONTRACT // const value = await _basic_oz.retrieve(); // console.log('State value is', value.toString());
• CALL TRANSACTION // await _basic_oz.store(23);

---

9) UNIT-TESTS ( chai.js)

npm install --save-dev chai

• /tests mirror /contracts 1 to 1.

create test/BASIC_oz.test.js npx truffle test

---

10) OZ TEST-HELPERS ( complex assertions )

npm install --save-dev @openzeppelin/test-helpers

• EXTRAs like
• veryify revert, exact balances, events emitted, time. // const { BN, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
• EXAMPLES:
• https://github.com/OpenZeppelin/openzeppelin-test-helpers/tree/master/test/src

---

11) ERC20, ERC721, ERC1155 ( standards )

###ERC20

###ERC721

• MINIMUM interface for SMARTCONTRACTS
• managed, owned, traded - TOKENS.
• unrestricted functions and metadata(!)
• multiple optional packages. LINK:https://eips.ethereum.org/EIPS/eip-721 ERC721 is ERC165 - NFT deed w/ unique ID. uint256

event Transfer - ownership transfer: created, distroyed event Approval - set approved address event ApprovalForAll - operator enabled, disabled, management. fn balanceOf - num NFTs owned by _owner fn ownerOf - _owner address fn safeTransferFrom - nft new _owner address confirm receiver. fn safeTransferFrom - additional data param fn transferFrom - unsafe caller nft ready 'to' assumed. fn approve - approved controller address, payable fn setApprovalForAll - authorized operators fn getApproved - get approved address fn isApprovedForAll -is authorized operator? ERC165, supportsInterface - wallet interface, safe trans ERC721TokenReceiver - after transfer receipt, allows transfer. onERC721Received - receipt hash *ERC721Metadata (optional) - name and details fn name fn symbol fn tokenURI - ipfs, metadata schema *ERC721Enumerable (optional)

• incremental and discoverable (full list)

fn totalSupply - count of nfts tracked fn tokenByIndex - enum item fn tokenByOwnerIndex - all assigned to _owner *ERC721URIStorage (optional) ERC721 is Context,IERC721,IERC721Metadata tokenId - must exist to verify allowed fn name fn symbol fn tokenURI fn _baseURI fn _safeTransfer - emit transfer event fn _exists fn _isApprovedOrOwner fn _safeMint fn _safeMint fn _mint fn _burn fn _transfer fn _approve - allows transfer, if not from fn _setApprovalForAll fn _checkOnERC721Received fn _beforeTokenTransfer

---

###ERC721-OPENZEPPELIN LINK: https://docs.openzeppelin.com/contracts/4.x/api/token/erc721

• INTERFACES, CONTRACTS, UTILITIES.
• Unopinion, Opinion: ERC721PresetMinterPauserAutoId

IERC721 - required to be ERC721 compliant. IERC721Metadata * IERC721Enumerable * IERC721Receiver - prevent locked tokens (verify receiver) ERC721Pausable - pause transfer ERC721Burnable - destroy ####CORE IERC721 event Transfer event Approval event ApprovalForAll fn balanceOf(owner), fn ownerOf(tokenId) fn safeTransferFrom(data), fn transferFrom fn approve - owner or operator fn getApproved - emits Approval Event fn setApprovalForAll, operator transfer fn isApprovedForAll, is operator allowed. ####IERC165 - supportsInterface ####IERC721Metadata name, symbol, tokenURI ####IERC721Enumerable totalSupply - total tokens tokenOfOwnerByIndex - tokenId by _owner at index

• use with balanceOf to enumerate all of owners tokens
• TODO similar mechanism to enumerate all creator tokens

tokenByIndex - tokenID at Index

• use with totalSupply to enum all tokens. ##ERC721 constructor(name_, symbol_) supportsInterface(interfaceId) balanceOf(owner) ownerOf(tokenId) name() symbol() tokenURI(tokenId) _baseURI() approve(to, tokenId) getApproved(tokenId) setApprovalForAll(operator, approved) isApprovedForAll(owner, operator) transferFrom(from, to, tokenId) safeTransferFrom(from, to, tokenId) safeTransferFrom(from, to, tokenId, _data) _safeTransfer(from, to, tokenId, _data)

_exists(tokenId) - tokenId exists? mint, exist, burn. _isApprovedOrOwner(spender, tokenId) - spender allowed? _safeMint(to, tokenId) - must be receiver _safeMint(to, tokenId, _data) _mint(to, tokenId) - unsafe use _safeMint _burn(tokenId) _transfer(from, to, tokenId) _approve(to, tokenId) _setApprovalForAll(owner, operator, approved) _beforeTokenTransfer(from, to, tokenId) HOOKS - called before and after (simplifies override) hook into original behavior - so far the only one!

• Rules of Hooks

virtual, always call parent hook using super. ####ERC721Enumerable ####ERC721Receiver ####ERC721Pausable - freezing all transfers. _beforeTokenTransfer - becomes pausible event Paused event Unpaused fn paused, _pause, _unpause ####ERC721Burnable ####ERC721URIStorage fn tokenURI fn setTokenURI fn burn ####ERC721PresetMinterPauserAutoId (opinion)

• Roles with AccessControl
• ROLES: ADMIN_ROLE, MINTER_ROLE, PAUSER_ROLE TODO: (CREATOR_ROLE)
• Deployer granted minter and pauser TODO: look to make this creator role.
• ACCESS CONTROL

fn getRoleMember fn getRoleMemberCount fn _grantRole fn _revokeRole fn hasRole fn _checkRole events roleChange, RoleGranted, RoleRevoked ###UTILITIES ###ERC721Holder fn onERC721Received.

---

###ERC1155

#CRYPTO-USE-CASES ###ERC721

• UNIQUE TOKENS.
• mint burn
• transfer and track
• sell token:
• auction, english, dutch
• buy token:
• ownership in wallet
• operators: brokers/auctioneers (consignment)
• Physical, Virtual, Negative