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做中国的V神!
Immutable(只可以再构造函数里修改)
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;
contract Immutable {
// coding convention to uppercase constant variables
address public immutable MY_ADDRESS;
uint public immutable MY_UINT;
constructor(uint _myUint) {
MY_ADDRESS = msg.sender;
MY_UINT = _myUint;
}
}
Ether and wei
Similar to how one dollar is equal to 100 cent, one ether is equal to 1018 wei.
1 wei is equal to 1
删除map中的值:用键删
function remove(address _addr) public { // Reset the value to the default value.
delete myMap[_addr]; }//这里是将那个索引处的值设置为默认值,不是把那个值删除!
二维度数组
mapping(address => mapping(uint => bool)) public nested;
指定长度或者是动态长度
uint[] public arr;
uint[] public arr2 = [1, 2, 3];
// Fixed sized array, all elements initialize to 0
uint[10] public myFixedSizeArr;
arr.push()/pop()/length
\
function examples() external {
// create array in memory, only fixed size can be created
uint[] memory a = new uint[](5);
}
\
数组右移动删除法
contract ArrayRemoveByShifting {
// [1, 2, 3] -- remove(1) --> [1, 3, 3] --> [1, 3]
// [1, 2, 3, 4, 5, 6] -- remove(2) --> [1, 2, 4, 5, 6, 6] --> [1, 2, 4, 5, 6]
// [1, 2, 3, 4, 5, 6] -- remove(0) --> [2, 3, 4, 5, 6, 6] --> [2, 3, 4, 5, 6]
// [1] -- remove(0) --> [1] --> []
uint[] public arr;
function remove(uint _index) public {
require(_index < arr.length, "index out of bound");
for (uint i = _index;
i < arr.length - 1; i++)
{ arr[i] = arr[i + 1];
}
arr.pop();
}
\
构造函数的两种构造方法:
todos.push(Todo(_text, false));
// key value mapping
todos.push(Todo({text: _text, completed: false}));
错误处理
import的使用方法
// import {symbol1 as alias, symbol2} from "filename";
import {Unauthorized, add as func, Point} from "./Foo.sol";//从一个地方分别抽取不同的方法
import http://...
ABI
adi其实就是函数选择器加上参数,转换为16进制编码
Hashing with Keccak256(这个我不是很懂)
keccak256 computes the Keccak-256 hash of the input.
Some use cases are:
- Creating a deterministic unique ID from a input
- Commit-Reveal scheme
- Compact cryptographic signature (by signing the hash instead of a larger input)
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;
contract HashFunction {
function hash(
string memory _text,
uint _num,
address _addr
) public pure returns (bytes32) {
return keccak256(abi.encodePacked(_text, _num, _addr));
}
// Example of hash collision
// Hash collision can occur when you pass more than one dynamic data type
// to abi.encodePacked. In such case, you should use abi.encode instead.
function collision(string memory _text, string memory _anotherText)
public
pure
returns (bytes32)
{
// encodePacked(AAA, BBB) -> AAABBB
// encodePacked(AA, ABBB) -> AAABBB
return keccak256(abi.encodePacked(_text, _anotherText));
}
}
contract GuessTheMagicWord {
bytes32 public answer =
0x60298f78cc0b47170ba79c10aa3851d7648bd96f2f8e46a19dbc777c36fb0c00;
// Magic word is "Solidity"
function guess(string memory _word) public view returns (bool) {
return keccak256(abi.encodePacked(_word)) == answer;
}
}
链下签名:solidity-by-example.org/signature/
这个搞不大来👆
