The Ultimate Solidity Course

Setting up Remix

Solidity is a typed language

The Most popular development framework in 2024

A quick overview of doing math in Solidity

A quick lesson on conditional operators

Syntax for iterative operators

Data types of unbounded size

2D and 3D data types

Using a “database in Web3”

Persistent lists

Persistent lists

Persistent hash maps with multiple levels

Determining which wallet is calling the smart contract

Configuring the smart contract on deployment

Protecting smart contracts from malicious parameters

An introduction to the most fundamental building block of DeFi

Batching values together

Solidity’s binary encoding format of choice

Learn how composability works in Solidity

Your first DeFi app

Transferring Ether with function calls

How smart contract can receive ETH transactions

What is the date and time today?

Leaving an audit trail in smart contracts

Organizing code in large smart contracts

Add re-useable functionality to Solidity function

Write-once variables

How to avoid “magic numbers”

Share your NFT with the world

Open source the code of an NFT

Convenient keywords for dealing with large numbers

How to keep data in groups

Concatenation, UTF-8 encoding, and more

How to write professional unit tests in Foundry

The purpose of this article is not to rehash the official Solidity Style Guide, which you should read.

Everyone makes mistakes, but some mistakes are more common than others.

You now have enough knowledge to build any of the following projects. Knowledge comes by study, but skill comes with practice.

This article describes three methods in Solidity for determining if an address is a smart contract:

The function selector is a 4 byte id that Solidity uses to identify functions under the hood.

ERC721 (or ERC-721) is the most widely used Ethereum standard for nonfungible tokens.

ERC4626 is a tokenized vault standard that uses ERC20 tokens to represent shares of some other asset.

An Enumerable ERC721 is an ERC721 with added functionality that enables a smart contract to list all the NFTs an address owns.

ERC-1363 enables a smart contract to detect and respond to an incoming transfer of tokens.

The uint256 max value can be obtained with type(uint256).max

Solidity signed integers enable using negative numbers in a smart contract. This article documents how they are used at the EVM level.

Staticcall is like a regular Ethereum call except that it reverts if a state change happens.

The onlyOwner modifier is probably one of the most common patterns in Solidity.

To test an internal solidity function, create a child contract that inherits from the contract being tested.

Solidity events are the closest thing to a “print” or “console.log” statement in Ethereum.

The purpose of this article is to describe the behavior of the solidity gasleft() function and its uses.

Reentrancy can only happen when your smart contract calls another smart contract via function call or sending ether.

Randomness is tricky on the blockchain because the blockchain is deterministic, but randomness requires non-determinism (otherwise it becomes predictable).

The MasterChef and Synthetix staking algorithms distribute a fixed reward pool among stakers according to their time-weighted contributions to a pool.

A fixed-point number is an integer that stores only the numerator of a fraction — while the denominator is implied.

Flash loans are loans between smart contracts that must be repaid in the same transaction.

Chainlink price oracles are smart contracts with public view functions that return the price of a particular asset denominated in USD.

The intuitive way to track lender deposits is to record the amount of USDC they deposited and the time they deposited. Compound V3 does not do this.

Uniswap is a DeFi app that enables traders to swap one token for another in a trustless manner.

his article explains how to determine the price settlement of a trading pair in an Automated Market Maker (AMM).

Uniswap V2’s swap function is cleverly designed, but many devs find its logic counterintuitive the first time they encounter it.

The lifecycle of Uniswap V2 is someone mints LP tokens (supplies liquidity, i.e. tokens to the pool) for the first time.

Uniswap V2 was designed to collect 1/6th of the swap fees to the protocol. Since a swap fee is 0.3%, 1/6th of that is 0.05%, so 0.05% of every trade would go to the protocol.

Suppose we have 1 Ether and 2,000 USDC in a pool. This implies that the price of Ether is 2,000 USDC.

The Uniswap V2 Library simplifies some interactions with pair contracts and is used heavily by the Router contracts.

The Router contracts provide a user-facing smart contract for safely minting and burning LP tokens (adding and removing liquidity)

It’s very educational to rebuild Uniswap v2 from scratch using modern Solidity (or Huff if you really want to do it in hard mode).

ABI encoding is the data format used for making function calls to smart contracts. It is also how smart contracts encode data when making calls to other smart contracts.

How storage variables work under the hood

A contract in Solidity can call other contracts via two methods: through the contract interface, which is considered a high-level call, or by using the call method, which is a low-level approach.

This article explains how delegatecall works in detail. The Ethereum Virtual Machine (EVM) offers four opcodes for making calls between contracts:

EIP 1967 is a standard for where to store information that proxy contracts need to execute.

ERC-7201 (formerly EIP-7201) is a standard for grouping storage variables together by a common identifier called a namespace.

The Transparent Upgradeable Proxy is a design pattern for upgrading a proxy while eliminating the possibility of a function selector clash.

EIP 1967 is a standard for where to store information that proxy contracts need to execute.

EIP-1167, which is also referred to as the minimal proxy contract, is a commonly used solidity pattern for cheaply creating proxy clones.

The minimal proxy standard allows us to parameterize the creation of the clone, but this requires an extra initialization transaction.

The nodelegatecall modifier prevents delegatecalls from being sent to a contract.

ERC20 Snapshot solves the problem of double voting.

ERC20 Votes does not actually handle conducting the poll, it’s still a regular ERC20 token with snapshot and delegated voting abilities.

The pattern of governance many DeFi applications follows is heavily inspired by Compound Finance’s implementation.

Compound is one of the most significant lending protocols in DeFi, having inspired the design of nearly every lending protocol on several blockchains.

The Compound V3 protocol measures interest on the scale of seconds. The Compound V3 frontend scales the number up to years for human friendliness.

The intuitive way to track lender deposits is to record the amount of USDC they deposited and the time they deposited.

The Compound V3 contract behaves like a rebasing ERC 20 token. A rebasing token is a token which has an algorithmically adjusted supply rather than a fixed one.

In this chapter we will examine the following topics about Compound V3: collateral valuation

Compound issues rewards in COMP tokens to lenders and borrowers in proportion to their share of the a market’s lending and borrowing.

The Uniswap V2 Library simplifies some interactions with pair contracts and is used heavily by the Router contracts.

The Router contracts provide a user-facing smart contract for safely minting and burning LP tokens (adding and removing liquidity)

The bulker contracts in Compound V3 are multicall-like contracts for batching several transactions.

The OG gas optimization course.

An Ethereum access list transaction enables saving gas on cross-contract calls by declaring in advance which contract and storage slots will be accessed.

Over 80 gas optimization tips and tricks.

When solidity generates the bytecode for the smart contract to be deployed, it appends metadata about the compilation at the end of the bytecode.

Smart contract creation cost can be anywhere from $10 to $2,000 assuming Ether costs between $1,500 to $2,000.

This article explains what happens at the bytecode level when an Ethereum smart contract is constructed and how the constructor arguments are interpreted.

EIP-150, or Ethereum Improvement Proposal 150, is a protocol upgrade for the Ethereum blockchain.

In this article, we will discuss invariants and how to perform an invariant test on solidity smart contracts using foundry test suites.

Mutation testing is a method to check the quality of the test suite by intentionally introducing bugs into the code and ensuring the tests catch the bug.

The second preimage attack in Merkle trees can happen when an intermediate node in a merkle tree is presented as a leaf.

Ethereum precompiles behave like smart contracts built into the Ethereum protocol. The nine precompiles live in addresses 0x01 to 0x09.

Creating a contract that gives certain addresses permissions goes by several names: airdrops, presale, whitelist, allowlist, and so forth.

Tornado cash is a cryptocurrency smart contract mixer that enables users to deposit crypto with one address and withdraw with another wallet.