Solidity Cheat Sheet

Transactions fields

• nonce: tx count for the account.
• gas price: price per unit of gas (in wei).
• gas limit: max gas that the tx can use.
• to: address that the tx is sent to.
• value: amount of wei to send.
• data: what to send to the TO address.
• v, r, s: components of tx signature.

Transactions - contract deployment

• nonce: tx count for the account.
• gas price: price per unit of gas (in wei).
• gas limit: max gas that the tx can use.
• to: empty.
• value: amount of wei to send.
• data: contract init code and contract bytecode.
• v, r, s: components of tx signature.

GAS - Ethereum Improvement Proposals (EIP) 1559

• Transaction Fee: Amount paid to the block producer for processing the transaction.

  • Gas used * Gas Price (Gwie)

• Gas Price: Cost per unit of gas specified for the transaction, in Ether and Gwei. The higher the gas price the higher chance of getting included in a block.

  • Base fee: the minimum gas price you need to set to include your transaction. Ends up getting burnt.
  • Max fee: refers to the maximum gas fee that we are willing to pay for the transaction.
  • Max priority fee: the max gas fee that we are willing to pay plus the max tip that we are willing to give to validators.

• Transaction fee - burnt fee = how much money went to validators.

Notes

• https://eth-converter.com/

• https://www.evm.codes/

• https://blog.openzeppelin.com/deconstructing-a-solidity-smart-contract-part-i-introduction-832efd2d7737

• https://openchain.xyz/signatures

• 1e18 = 1 ETH = 1 * 10 ** 18.

• 'Receive/Fallback' special functions: The receive function is specifically designed to handle Ether transfers without data and is automatically invoked when Ether is sent to the contract in a transaction with no call data (msg.data is empty). The fallback function is used for handling calls with data or when the receive function is not defined. The fallback function can also handle Ether transfers with data.

    // Explainer from: https://solidity-by-example.org/fallback/
    // Ether is sent to contract
    //      is msg.data empty?
    //          /   \ 
    //         yes  no
    //         /     \
    //    receive()?  fallback() 
    //     /   \ 
    //   yes   no
    //  /        \
    //receive()  fallback()

EVM Transaction Types

Type Identifier	Common Name	Defining EIP	Key Features
0x0	Legacy Transaction	(Pre-EIP-2718)	The original format. Uses a single gasPrice field.
0x1	Access List Transaction	EIP-2930	Adds an accessList to specify addresses and storage keys the transaction will access, potentially reducing gas costs for complex interactions. Still uses gasPrice.
0x2	EIP-1559 Transaction	EIP-1559	The modern standard. Replaces gasPrice with maxPriorityFeePerGas (the tip) and maxFeePerGas. The baseFee is burned. Also supports accessList.
0x3	Blob Transaction	EIP-4844	Introduced for Layer 2 rollups (Proto-Danksharding). Adds fields for handling "blobs" of data (maxFeePerDataGas, blobVersionedHashes) to drastically reduce data-posting costs for L2s.

Transaction status

1. Pending: This is the initial state after you submit a transaction. It has been successfully broadcast to the network and is waiting in the "mempool" (a memory pool of pending transactions) to be picked up by a validator.

2. Mined (or Confirmed): A validator has included your transaction in a new block, and that block has been successfully added to the blockchain. At this point, the transaction is permanent. A mined transaction also has a sub-status: either Success or Failed (Reverted). A failed transaction was still included in a block and you still paid the gas fee, but the contract's code execution failed (e.g., a require statement was not met).

3. Replaced / Dropped: This is the other major possibility. This status means your transaction was removed from the mempool without being mined. This typically happens for two reasons:

   • Replaced: You (or your wallet software) submitted a new transaction with the exact same nonce but a higher gas fee. The network recognizes this as an intentional replacement, discards your original, slower transaction from the mempool, and prioritizes the new, more expensive one. This is a common way to "speed up" or "cancel" a stuck transaction.

   • Dropped: If your transaction's gas fee is too low to ever be picked up during a period of high network congestion, network nodes may eventually "drop" it from their individual mempools to make space for new, higher-fee transactions. If your transaction is dropped from enough nodes, it effectively disappears from the network without ever being mined or replaced.

Order of layout

Layout of Contract

• version
• imports
• errors
• interfaces, libraries, contracts
• Type declarations
• State variables
• Events
• Modifiers
• Functions

Layout of Functions:

• constructor
• receive function (if exists)
• fallback function (if exists)
• external
• public
• internal
• private
• view & pure functions

Ethereum Request for Comments (ERC)

ERC-20

• ERC-20 Token Standard: It´s an smart contract that represent a token.
• Governance tokens.
• Secure an underlying network.
• Create a synthetic asset.

ERC-721 (NFT - Non-Fungible Token)

• Token URI.
• Metadata: an endpoint return the metadata.

IPFS

• Decentralized storage (nodes optionally choose what to pin)
• our code -> hash it

Testnet faucets

• Google
• Chainlink