Solidity 基础语法

1// SPDX-License-Identifier: MIT
2pragma solidity ^0.8.20;
3 
4/**
5 * @title SimpleStorage
6 * @dev 演示基础数据类型和函数
7 */
8contract SimpleStorage {
9    // 状态变量（存储在 storage）
10    uint256 private favoriteNumber;
11    address public owner;
12    
13    // 结构体
14    struct Person {
15        string name;
16        uint256 age;
17    }
18    
19    // 映射
20    mapping(address => Person) public people;
21    
22    // 事件
23    event NumberUpdated(uint256 indexed oldNumber, uint256 indexed newNumber, address updater);
24    
25    // 修饰器
26    modifier onlyOwner() {
27        require(msg.sender == owner, "Not owner");
28        _;
29    }
30    
31    // 构造函数
32    constructor() {
33        owner = msg.sender;
34    }
35    
36    // 公共函数
37    function setNumber(uint256 _number) external onlyOwner {
38        uint256 oldNumber = favoriteNumber;
39        favoriteNumber = _number;
40        emit NumberUpdated(oldNumber, _number, msg.sender);
41    }
42    
43    // 视图函数（不修改状态）
44    function getNumber() external view returns (uint256) {
45        return favoriteNumber;
46    }
47    
48    // 纯函数（不读取状态）
49    function add(uint256 a, uint256 b) external pure returns (uint256) {
50        return a + b;
51    }
52}

1contract DataLocation {
2    struct LargeData {
3        uint256 id;
4        string name;
5        bytes data;
6    }
7    
8    LargeData[] public items;
9    
10    // ❌ 低效：复制到 memory
11    function inefficientUpdate(uint256 index) external {
12        LargeData memory item = items[index];
13        item.id = 999;
14        items[index] = item; // 整个结构体写回
15    }
16    
17    // ✅ 高效：直接操作 storage
18    function efficientUpdate(uint256 index) external {
19        LargeData storage item = items[index];
20        item.id = 999; // 只修改一个字段
21    }
22    
23    // calldata：只读，最省 Gas
24    function processData(string calldata _text) external pure returns (uint256) {
25        return bytes(_text).length;
26    }
27}

1contract ErrorHandling {
2    error InsufficientBalance(uint256 requested, uint256 available);
3    error Unauthorized(address caller);
4    
5    mapping(address => uint256) public balances;
6    address public admin;
7    
8    // ✅ 推荐：自定义错误（省 Gas）
9    function withdraw(uint256 amount) external {
10        if (balances[msg.sender] < amount) {
11            revert InsufficientBalance({
12                requested: amount,
13                available: balances[msg.sender]
14            });
15        }
16        balances[msg.sender] -= amount;
17        payable(msg.sender).transfer(amount);
18    }
19    
20    // ⚠️ require：适合简单条件检查
21    function setAdmin(address newAdmin) external {
22        require(msg.sender == admin, "Only admin");
23        admin = newAdmin;
24    }
25    
26    // ⚠️ assert：用于不变量检查（会消耗所有剩余 Gas）
27    function internalTransfer(address from, address to, uint256 amount) internal {
28        balances[from] -= amount;
29        balances[to] += amount;
30        assert(balances[from] + balances[to] >= amount); // 溢出检查
31    }
32}