0x01 大量參數(shù)的問(wèn)題
隨著智能合約要處理的問(wèn)題越來(lái)越復(fù)雜，引入的配置參數(shù)也越來(lái)越多，這些配置參數(shù)通常作為狀態(tài)變量放在合約里，并且需要引入管理員權(quán)限來(lái)設(shè)置這些變量。通常我們都是像下面這個(gè)代碼一樣去處理這些變量：
address public token;
uint256 public minAmount;
uint256 public maxSize;
bytes32 public hash;
event SetToken(address oldToken, address newToken);
event SetMinAmount(uint256 oldMinAmount, uint256 newMinAmount);
event SetMaxSize(uint256 oldMaxSize, uint256 newMaxSize);
event SetHash(bytes32 oldToken, bytes32 newHash);
function setToken(address _token) external onlyAdmin {
emit SetToken(token, _token);
token = _token;
}
function setMinAmount(uint256 _minAmount) external onlyAdmin {
emit SetMin(minAmount, _minAmount);
min = _min;
}
function setMaxSize(uint256 _maxSize) external onlyAdmin {
emit SetMax(maxSize, _maxSize);
max = _max;
}
function setHash(bytes32 _hash) external onlyAdmin {
emit SetHash(hash, _hash);
hash = _hash;
}
這種寫法，一個(gè)變量配一個(gè)事件一個(gè) setter, 正常工作是沒啥問(wèn)題的，只是隨著變量數(shù)量的增加，代碼膨脹起來(lái)會(huì)非?？?，并且看起來(lái)都是些類似的代碼。
0x02 合并參數(shù)設(shè)置
為了減少這些模版代碼，有一種做法是把設(shè)置方法合并，就像下面這樣：
function setParameters(address _token, uint256 _minAmount, uint256 _maxSize, bytes32 _hash) external onlyAdmin {
......
}
這確實(shí)可以減少一些模版代碼，但帶來(lái)的最直接的問(wèn)題就是每次都要把所有參數(shù)都設(shè)置一遍，帶來(lái)誤設(shè)參數(shù)的風(fēng)險(xiǎn)。
0x03 對(duì)參數(shù)進(jìn)行類型抽象
另外一種做法是對(duì)參數(shù)進(jìn)行類型抽象，就像下面這樣：
address public token;
uint256 public minAmount;
uint256 public maxSize;
bytes32 public hash;
event SetParameter(bytes32 parameter, bytes value);
error InvalidParameter(bytes32 parameter);
function setParameter(bytes32 parameter, bytes calldata value) external onlyAdmin {
if (parameter == "token") token = abi.decode(value, (address));
else if (parameter == "minAmount") minAmount = abi.decode(value, (uint256));
else if (parameter == "maxSize") maxSize = abi.decode(value, (uint256));
else if (parameter == "hash") hash = abi.decode(value, (bytes32));
else revert InvalidParameter(parameter);
emit SetParameter(parameter, value);
}
這種寫法，代碼看起來(lái)更緊湊了，代價(jià)就是設(shè)置參數(shù)的時(shí)候要確定參數(shù)名稱，并且對(duì)參數(shù)的值進(jìn)行 encode 處理。
如果不想對(duì)參數(shù)進(jìn)行編碼處理，可以使用對(duì)不同類型參數(shù)進(jìn)行重載的方式，像下面這樣：
function setParameter(bytes32 parameter, address value) external onlyAdmin {
if (parameter == "token") token = abi.decode(value, (address));
else revert InvalidParameter(parameter);
emit SetParameter(parameter, abi.encode(value));
}
function setParameter(bytes32 parameter, uint256 value) external onlyAdmin {
if (parameter == "minAmount") minAmount = abi.decode(value, (uint256));
else if (parameter == "maxSize") maxSize = abi.decode(value, (uint256));
else revert InvalidParameter(parameter);
emit SetParameter(parameter, abi.encode(value));
}
function setParameter(bytes32 parameter, bytes32 value) external onlyAdmin {
if (parameter == "hash") hash = abi.decode(value, (bytes32));
else revert InvalidParameter(parameter);
emit SetParameter(parameter, abi.encode(value));
}
參數(shù)也可以使用 enum 類型，像下面這樣
enum ParameterType {
NotSupported,
Token,
MinAmount,
MaxSize
Hash
}
function setParameter(ParameterType parameter, bytes calldata value) external onlyAdmin {
if (parameter == ParameterType.Token) token = abi.decode(value, (address));
else if (parameter == ParameterType.MinAmount) minAmount = abi.decode(value, (uint256));
else if (parameter == ParameterType.MaxSize) maxSize = abi.decode(value, (uint256));
else if (parameter == ParameterType.Hash) hash = abi.decode(value, (bytes32));
else revert InvalidParameter(parameter);
emit SetParameter(parameter, value);
}
0x04 file 模式
上面的這種做法，也被稱作 file 模式，在幾個(gè)項(xiàng)目里都有體現(xiàn)
比如在 MakerDAO 的這個(gè)代碼里](https://github.com/makerdao/dss/blob/fa4f6630afb0624d04a003e920b0d71a00331d98/src/vat.sol#L104)%E9%87%8C)，就有下面的代碼片段：
function file(bytes32 what, uint data) external auth {
require(live == 1, "Vat/not-live");
if (what == "Line") Line = data;
else revert("Vat/file-unrecognized-param");
}
function file(bytes32 ilk, bytes32 what, uint data) external auth {
require(live == 1, "Vat/not-live");
if (what == "spot") [ilks[ilk].spot](http://ilks[ilk].spot/) = data;
else if (what == "line") ilks[ilk].line = data;
else if (what == "dust") ilks[ilk].dust = data;
else revert("Vat/file-unrecognized-param");
}
在 Astaria 的這個(gè)代碼里](https://github.com/AstariaXYZ/astaria-core/blob/f4be95017b09dd5b78741cdffae4e07c0b06f68b/src/LienToken.sol#L82)%E9%87%8C)，有下面的代碼片段：
function file(File calldata incoming) external requiresAuth {
FileType what = incoming.what;
bytes memory data = incoming.data;
LienStorage storage s = _loadLienStorageSlot();
if (what == FileType.CollateralToken) {
s.COLLATERAL_TOKEN = ICollateralToken(abi.decode(data, (address)));
} else if (what == FileType.AstariaRouter) {
s.ASTARIA_ROUTER = IAstariaRouter(abi.decode(data, (address)));
} else {
revert UnsupportedFile();
}
emit FileUpdated(what, data);
}
0x05 總結(jié)
當(dāng)合約里需要維護(hù)大量配置參數(shù)時(shí)，通常的寫法會(huì)讓合約代碼快速膨脹，這時(shí)可以采用對(duì)參數(shù)進(jìn)行編碼的方式使代碼更加緊湊，不過(guò)具體采用哪種寫法，還要看具體情況而定。
