0. 版本

[openzeppelin]：v4.8.3，[forge-std]：v1.5.6

0.1 ERC20Capped.sol

Github: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/token/ERC20/extensions/ERC20Capped.sol

ERC20Capped庫是ERC20的拓展。該庫設置了ERC20發行量的上限。

1. 目標合約

繼承ERC20Capped合約：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/src/token/ERC20/extensions/MockERC20Capped.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;import "openzeppelin-contracts/contracts/token/ERC20/extensions/ERC20Capped.sol";contract MockERC20Capped is ERC20Capped {constructor(string memory name, string memory symbol, uint cap)ERC20(name, symbol)ERC20Capped(cap){}function mint(address account, uint amount) external {_mint(account, amount);}
}

全部foundry測試合約：

Github: https://github.com/RevelationOfTuring/foundry-openzeppelin-contracts/blob/master/test/token/ERC20/extensions/ERC20Capped.t.sol

2. 代碼精讀

2.1 constructor() && cap()

• constructor()：初始化函數對發行量上限進行了設置；
• cap()：返回ERC20發行量上限

	// token發行量上限（immutable類型，合約初始化后無法再更改）uint256 private immutable _cap;constructor(uint256 cap_) {// 要求設置的發行量上限大于0require(cap_ > 0, "ERC20Capped: cap is 0");// 設置上限_cap = cap_;}function cap() public view virtual returns (uint256) {// 返回常量_cap的值return _cap;}

foundry代碼驗證：

contract ERC20CappedTest is Test {MockERC20Capped private _testing = new MockERC20Capped("test name", "test symbol", 100);function test_Constructor() external {assertEq(_testing.cap(), 100);// revert with 0 cap in constructorvm.expectRevert("ERC20Capped: cap is 0");new MockERC20Capped("test name", "test symbol", 0);}
}

2.2 _mint(address account, uint256 amount)

為account地址鑄造數量為amount的token。

    function _mint(address account, uint256 amount) internal virtual override {// 檢查本次mint后的總發行量不得大于發行量上限require(ERC20.totalSupply() + amount <= cap(), "ERC20Capped: cap exceeded");// 調用ERC20.mint()進行鑄造super._mint(account, amount);}

foundry代碼驗證：

contract ERC20CappedTest is Test {MockERC20Capped private _testing = new MockERC20Capped("test name", "test symbol", 100);address private user = address(1);function test_Mint() external {_testing.mint(user, 100);assertEq(_testing.totalSupply(), 100);vm.expectRevert("ERC20Capped: cap exceeded");_testing.mint(user, 1);}
}

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