详解函数动态调用的作用—

详解函数动态调用的作用——call

动态调用的作用

类似于其他语言的反射
能够开发框架性代码

Call调用语法

(bool success, bytes data) = <address>.call(bytes calldata)

call是address的方法
call返回值(bool success, bytes data)
忽视返回值success，会造成严重问题

calldata的结构

call的参数是calldata
calldata的前四个字节是selector，剩下的是参数编码
selector = bytes(keccak256())
keccak256:哈希sha3->256

Abi工具函数

calldata = abi.encodeWithSignature(sig, ps)–会用
返回值解码abi.decode(bytes)

编码、解码 decoder.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;contract AbiDecode {struct MyStruct {string name;uint[2] nums;}function encode(uint x,address addr,uint[] calldata arr,MyStruct calldata myStruct) external pure returns (bytes memory) {return abi.encode(x, addr, arr, myStruct);}function decode(bytes calldata data)externalpurereturns (uint x, address addr, uint[] memory arr, MyStruct memory myStruct){// (uint x, address addr, uint[] memory arr, MyStruct myStruct) = ...(x, addr, arr, myStruct) = abi.decode(data, (uint, address, uint[], MyStruct));}
}

效果：
在这里插入图片描述
Callee.sol

// SPDX-License-Identifier: GPL-3.0pragma solidity >=0.8.2 <0.9.0;contract Callee {uint public x;function setX(uint _x)public returns(uint){x = _x;return x;}
}

Caller.sol

// SPDX-License-Identifier: GPL-3.0pragma solidity >=0.8.2 <0.9.0;contract Caller{address calleeAddress;uint public xx;constructor(address _calleeAddress){calleeAddress = _calleeAddress;}function setCalleeX(uint _x)public{bytes memory cd = abi.encodeWithSignature("setX(uint256)", _x);(bool suc, bytes memory rst) = calleeAddress.call(cd);if(!suc){revert("call failed");}(uint x) = abi.decode(rst, (uint));xx = x;}
}