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Robin

  1. 自我介绍
    大家好我是Robin(cxk228922)，一名正在台灣就讀高二的學生，對資訊安全頗有興趣
    之前都是往計算機本身漏洞探究，想慢慢跨進到網路相關的內容。
  2. 你认为你会完成本次残酷学习吗？
    我會盡我所能完成一切

Notes

這邊先和助教說聲抱歉，由於我最近課業繁忙，並且對網路、區塊鏈並沒有基礎，每天能學習的內容有限><。以及我想趁此機會練習英文，文法可能有許多不妥處，可能有點難以閱讀。

2024.09.23

  1. Remix IDE
  • File Extension of Solidity : .sol
  • Ctrl + S -> Compile
  • Deploy -> Simulate Ethereum chain -> run smart contracts
  1. Basic
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.21;
contract HelloWeb3{
    string public _string = "Hello Web3!";
}
  • // SPDX-License-Identifier: MIT -> Denotes license identifier (MIT for example)
  • pragma solidity ^0.8.21; -> Only allow compiler version 0.8.21 ~ 0.9.0(0.8.21 for example)
  • contract HelloWeb3 -> Similar as class in other programming language (HelloWeb3 for example). also,we call it "合約"
  • string public _string = "Hello Web3!"; -> Declared Variables
  • string : Value type
Type Explain Example
int integer 3 , 300 , -123
uint unsigned integer(include 0) 3 , 300
uint k-bit unsigned integer uint8 , uint64
bool boolean true , false
address address(e.g. ETH account) 0x1234556
enum enumeration {Mon=1,Tue,Wed}
  • public : visibility
Type Outside Contract In Contract Inheritance Contract
public ✅ ✅ ✅
private ❌ ✅ ❌
external (function) ✅ ✅use this.func() ✅use this.func()
internal ❌ ✅ ✅
  • _string : Value name,Define by your self
  • "Hello Web3!" : Value
function <functionName>(<Type> <ParameterName>) <visibility> <modifier> returns (<Type>)

<Type> <parameter1> : Input parameter,e.g. int a      Also,you can input more than 1 parameter

<modifier> :

Value Explain
pure cannot read nor write
view can read but cannot write
(NULL) can both read and write
payable can receive ETH

2024.09.24

  1. Variables

data storage locations:

Type stored modified
storage(deafult) on-chain ✅
memory in memory ✅
calldata in memory ❌(read-only)

scope:

contract Example {
    uint public count;
    function increment() public pure returns (uint) {
        uint localCount = 0; 
        return localCount;
    }
}
Type Location Complain/Example
State(狀態變量) storage count(in contract storage)
Local(局部變量) memory(reference types)
stack(basic types)		 localCount(in function)
Global(全局變量) EVM dynamic msg.sender,block.number
  1. Array
//fixed-sized arrays
<type>[<length>] <name>;
<type>[] memory <name> = new <type>[](<length>);
uint[9] array;
uint[] memory array3 = new uint[](5);

//dynamic-sized array
uint[] array1;
bytes array2;    //dynamic byte array
  • .length -> return array's length dynamic array :
  • .push -> add 0element at the end of array
  • .puxh(x) -> add xelement at the end of array
  • .pop -> remove the last element of array
  1. Struct
struct Student{
    uint id;
    uint score; 
}
//4 ways to assign value
function method1() external{
    Student storage _student = student; //copy Student
    _student.id = 11;
    _student.score = 100;
}
function method2() external{
    student.id = 1;
    student.score = 80;
}
function method3() external {
    student = Student(3, 90);
}
function method4() external {
    student = Student({id: 4, score: 60});
}
  1. Map key -> Value
mapping(<KeyType> => <ValueType>) public <name>;
mapping(address => uint) public balances;

<name>[<key>] = <Value>;
balances[msg.sender] = 100;

2024.09.25

  1. constant/immutable
Characteristic constant immutable
Initialization time declaration constructor/declaration
Modification time Compile-time constant Determined at deployment
Storage location Inlined directly at compile-time storage
Use cases completely fixed values (e.g. fixed rates) values determined by conditions at deployment time (e.g.deployer)
  1. Control flow
    as same as C
//if-else
function ifElseTest(uint256 _number) public pure returns(bool){
    if(_number == 0){
        return(true);
    }else{
        return(false);
    }
}
//for loop
function forLoopTest() public pure returns(uint256){
    uint sum = 0;
    for(uint i = 0; i < 10; i++){
        sum += i;
    }
    return(sum);
}
//while
function doWhileTest() public pure returns(uint256){
    uint sum = 0;
    uint i = 0;
    do{
        sum += i;
        i++;
    }while(i < 10);
    return(sum);
}
//Insertion Sort
function insertionSort(uint[] memory a) public pure returns(uint[] memory) {
    for (uint i = 1;i < a.length;i++){
        uint temp = a[i];
        //uint j=i-1;
        uint j=i;    //uint can't <0
        while( (j >= 1) && (temp < a[j-1])){    
        //before:(temp < a[j])
            a[j] = a[j-1];
            j--;
        }
        a[j] = temp;
    }
    return(a);
}

2024.09.27

  1. constructor If variables is dynamic dicision when deploy,we can use constructor to assign (similar as decorator)
address owner; 
constructor(address initialOwner) {
    owner = initialOwner; 
}
  1. modifier use to modify the behavior of function
address public owner;
bool public paused;

constructor() {
	owner = msg.sender;
	paused = false;
}

modifier onlyOwner() {
	require(msg.sender == owner, "Not authorized");
	_;//continue to run function
}

modifier whenNotPaused() {
	require(!paused, "Contract is paused");
	_;
}

function setPause(bool _paused) public onlyOwner {
	paused = _paused;
}

function changeOwner(address newOwner) public onlyOwner whenNotPaused {
	owner = newOwner;
}
  1. event When event be triggered,it will be recorded in log
event Transfer(address indexed from, address indexed to, uint256 value);

function transfer(address _to, uint256 _value) public {
    emit Transfer(msg.sender, _to, _value);    //trigger event
}
  1. override OverWrite the parent function
contract Parent {
    function foo() public virtual {
    }
}

contract Child is Parent {
    function foo() public override {
        //...
    }
}

2024.09.29

  1. Interface Define the interactions between contracts
interface Token {
    function transfer(address recipient, uint256 amount) external returns (bool);
}

contract MyToken is Token {
    mapping(address => uint256) public balances;

    function transfer(address recipient, uint256 amount) external override returns (bool) {
        require(balances[msg.sender] >= amount, "Insufficient balance");
        balances[msg.sender] -= amount;
        balances[recipient] += amount;
        return true;
    }
}

1.1 IERC721

  • event-Transfer:
event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

when tokenID moved from from to another address to

  • event-ApprovalForAll:
event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

The token holder authorizes/de-authorizes an operator to manage all its tokens.

  • function-balanceOf
function balanceOf(address owner) external view returns (uint256 balance);

return the number of tokens owned by owner

  • function-ownerOf
function ownerOf(uint256 tokenId) external view returns (address owner);

return the address of owner of tokenID

and more....

2024.09.30

  1. Error Handling
  • require Used to check if a condition is true
    If false,contract will be terminated
function withdraw(uint amount) public {
    require(amount <= balance, "Insufficient balance");
    balance -= amount;
    payable(msg.sender).transfer(amount);
}
  • assert Used to check if a condition always be true
function decrement() public {
    assert(counter > 0);
    counter -= 1;
}
  • error Custom error
error InsufficientBalance(uint requested, uint available);

function withdraw(uint amount) public {
    if (amount > balance)
        revert InsufficientBalance({
            requested: amount,
            available: balance
        });
    balance -= amount;
    payable(msg.sender).transfer(amount);
}

2024.10.02

overloading

You can define 2 or more same-name function (except modifier)
but need to be different input type

function saySomething() public pure returns(string memory){
    return("Nothing");
}

function saySomething(string memory something) public pure returns(string memory){
    return(something);
}

Argument Matching

function f(uint8 _in) public pure returns (uint8 out) {
    out = _in;
}

function f(uint256 _in) public pure returns (uint256 out) {
    out = _in;
}

if we call f(123),it can be uint8 anduint256,the compiler will report error

2024.10.03

Library

Like "Header file" in C++ , a function collection e.g. Strings

using Strings for uint256;
function getString1(uint256 _number) public pure returns(string memory){
    return _number.toHexString();
}

or

function getString2(uint256 _number) public pure returns(string memory){
    return Strings.toHexString(_number);
}

tips...

  • Non-storable state variable
  • Unable to receive ETH
  • Can't be destroyed

Import

If we have...

Dir
├── Import.sol
└── Yeye.sol

We can use import to include contracts/library... in external file

import './Yeye.sol';

other option:

//only a part that needed 
import { ContractName1, ContractName2 } from "path/to/file.sol";

//as to rename
import { ContractName as Alias } from "path/to/file.sol";

//package manager
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

//URL
import "https://github.com/username/repo/blob/main/Contract.sol";

2024.10.04

receive ETH

event Received(address Sender, uint Value);
receive() external payable {
    emit Received(msg.sender, msg.value);
}
  • can't have any parameters
  • can't return anything
  • need to be external and payable

fallback

  • If the contract only has receive && transaction doesn't have calldata -> receive()
  • If the contract has fallback && (transaction has calldata || no corresponding function) -> fallback()

2024.10.08

Calling via Contract Address:

Use the contract address to create a reference and call the target contract's function.

function callSetX(address _Address, uint256 x) external {
    OtherContract(_Address).setX(x);
}

Passing Contract Reference:

Pass the target contract reference directly and call its functions.

function callGetX(OtherContract _Address) external view returns (uint x) {
    x = _Address.getX();
}

Creating Contract Variable:

Create a contract variable within the function to call the target's functions.

Copy code
function callGetX2(address _Address) external view returns (uint x) {
    OtherContract oc = OtherContract(_Address);
    x = oc.getX();
}

Calling payable Function and Sending ETH:

Call a payable function and transfer ETH using {value: msg.value}.

Copy code
function setXTransferETH(address otherContract, uint256 x) payable external {
    OtherContract(otherContract).setX{value: msg.value}(x);
}

2024.10.10

delegatecall

  • low-level function
  • executes the code of another contract in the context of the calling contract.
contract LogicContract {
    uint public number;

    function setNumber(uint _num) public {
        number = _num;
    }
}

contract ProxyContract {
    uint public number;

    function setNumber(address _logicContract, uint _num) public {
        (bool success, ) = _logicContract.delegatecall(
            abi.encodeWithSignature("setNumber(uint256)", _num)
        );
        require(success, "delegatecall failed");
    }
}