Solidity Cheat Sheet - Every Pattern You Need (2026)

Solidity Cheat Sheet - Every Pattern You Need (2026)

Complete Solidity reference. Types, functions, modifiers, events, security.

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Data Types

uint256, int256, address, string, bytes32, bool

Mapping: mapping(address => uint256) public balances;

Array: uint256[] public items;

Struct: struct User { address wallet; uint256 balance; bool active; }

Functions

public view - Read, no gas

public pure - No state read

public payable - Accepts ETH

external - Only callable from outside

internal - Contract + children only

private - This contract only

Modifiers

modifier onlyOwner() { require(msg.sender == owner); _; }

modifier costs(uint price) { require(msg.value >= price); _; }

Events

event Transfer(address indexed from, address indexed to, uint256 amount);

emit Transfer(msg.sender, to, amount);

Security

Checks-Effects-Interactions: Check first, update state, then interact

Reentrancy: bool locked; modifier noReentrant { require(!locked); locked=true; _; locked=false; }

Safe transfer: (bool ok,) = to.call{value: amount}(""); require(ok);

ERC20 Pattern

mapping(address => uint256) public balanceOf;

function transfer(address to, uint amount) public { require(balanceOf[msg.sender] >= amount); balanceOf[msg.sender] -= amount; balanceOf[to] += amount; }

Deploy with Foundry

forge init my-contract && forge build && forge test

forge create src/Contract.sol:MyContract --rpc-url $RPC --private-key $KEY

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