Ethereum / Solidity

Development

Development Workflow (Truffle, Hardhat)

with Truffle

Truffle is a CLI tool. The workflow is like this:

Start a Truffle project with truffle init Run a local development Blockchain with truffle develop (Truffle comes with its own version of Ganache) Deploy your smart contract with truffle migrate --reset (the reset flag is necessary to avoid some caching problems) Run smart contract test with truffle test (includes web3 and BN.js) Deploy your frontend

Hardhat

• https://hardhat.org/getting-started/
• https://hardhat.org/tutorial/testing-contracts.html

Dependencies: If using "@openzeppelin/test-helpers", then "require("@nomiclabs/hardhat-web3")"

Nodes (Infura, Alchemy)

How to use Infura?

To deploy a smart contract to Infura you need to:

Create a project in Infura Fund the deployment address (using a faucet in the case of testnet) Add a configuration for this deployment in the configuration file of your Truffle project Run the deployment with Truffle (ex: truffle migrate --reset --network ropsten) We will see this in details later in this course in the section on smart contract deployment.

Alchemy

Free tier includes archival nodes

Custom Scaffold

./compile.js ./test/ ./contracts/

• Manual Set Up (without framesworks):

  • solidity compiler: solc
  • testing: mocha
  • local network + provider: ganache-cli
  • integrating client with network (deploy new or interact with existing contract): web3

• Remix:

  • web IDE
  • manual testing
  • compile / deployment

• Truffle:

  • contract creation
  • automated testing (JS: mocha, Solidity)
  • deploying to networks

Test Networks

Infura or host own node

• Ropsten:
  • most similar to main net ∴ use occasionally
  • slow block times
• Rinkeby:
  • least similar to main net than Ropsten ∴ use frequently
  • fast block times

Notes

• gasPrice (Wei/gas): amount of Wei the sender is willing to pay per unit of gas
• startGas/gasLimit (gas): total units of gas willing to spend for the transaction

Gotchas

• Contract Functions:
  • call()
    • cannot modify data
    • returns data instantly from node (does not require processing a new block)
  • Nested Dynamic Arrays
    • OK in Solidity
    • Doesn't work in ABI/JS/Web3
    • String are stored as an array of chars ∴ an Array of Strings
    • experimental feature: pragma experimental ABIEncoderV2;

Security:

• https://consensys.github.io/smart-contract-best-practices/
• https://arxiv.org/pdf/1806.01143.pdf

Articles:

Ethereum basics

Intro - https://blog.b9lab.com/unpacking-the-ethereum-stack-for-developers-c1be1dc41c06

Data structures

Basic CRUD - https://medium.com/robhitchens/solidity-crud-part-1-824ffa69509a Simply State Machine - https://medium.com/coinmonks/state-machines-in-solidity-9e2d8a6d7a11

Forking mainnet and other public networks:

Compound Example - https://medium.com/compound-finance/supplying-assets-to-the-compound-protocol-ec2cf5df5aa

Upgrading Smart Contracts:

https://github.com/jklepatch/eattheblocks/tree/master/screencast/372-smart-contract-upgrade

• Proxy Pattern: minimal proxy contract has a fallback(), contract requires assembly, memory of versions dependent on each other
• Adapter Pattern: main contract contains state and the functions but calls another contract for certain implementation logic. Implementation can be upgraded over time (ex. Yearn strategies).
• Migrator: New version is deployed with a migrator contract. Addresses can call the migrator contract to transfer state from older version to new version. This is a common pattern for tokens.