Sep 29 , 2020

What are Ethereum Transactions?

Transaction Types and Data Model

Understanding the anatomy of a transaction is pivotal for success in Ethereum development.

Transaction Data Model

Nonce: Transaction counter of the sender
Gas Price: Price paid per unit of gas
Gas Limit: Maximum gas provided for the transaction
To: Recipient address or contract address
Value: Amount of ether sent in the transaction
Data: Input data for contract transactions
v, r, s: Components of the transaction signature

Example:

{
  from: "0xEA674fdDe714fd979de3EdF0F56AA9716B898ec8",
  to: "0xac03bb73b6a9e108530aff4df5077c2b3d481e5a",
  gasLimit: "21000",
  maxFeePerGas: "300",
  maxPriorityFeePerGas: "10",
  nonce: "0",
  value: "10000000000",
  data: null,
}

Types of Transactions

Value Transfer

Gas Limit: Typically 21,000
Description: Transfer ether from one account to another.
Details: Doesn't modify the blockchain's state. Recipients can be Externally Owned Accounts (EOA) or Contracts.

Contract Deployment

Description: Deploy a new smart contract onto the blockchain.
Details: Requires transaction data to contain the bytecode of the contract being deployed.

Function Call

Description: Invoke a function within a deployed contract.
Details: Can modify the state of the blockchain. These transaction types and their associated data models are crucial for executing different operations on the Ethereum blockchain, managing smart contracts, and transferring ether between accounts.

ABI Encoding

To encode function calls to send to smart contracts, expecting those smart contract to interpret that message and consequently run the code you want.

Account to Contract
Contract to Contract
- Contract can call other contracts in 2 ways: a) A.foo(x, y, z) b) use the low-level call (not recommended)

Caller:

mutable arguments
encode arguments
what are callee's apis? a) The Function Signature b) The Function Selector
- first 4 bytes of function signature
- how to get?
  - The first 4 bytes returned from abi.encodeWithSignature(....) is the function selector.


    addr.call(abi.encodeWithSignature("transfer(address,uint256)", 0xSomeAddress, 123))

    contract FunctionSelector {
        /*
        "transfer(address,uint256)"
        0xa9059cbb
        "transferFrom(address,address,uint256)"
        0x23b872dd
        */
        function getSelector(string calldata _func) external pure returns (bytes4) {
            return bytes4(keccak256(bytes(_func)));
        }
    }