在0.6.8版本的solidity中使用delegatecall进行合约升级

在0.4.26版本的solidity中，delegatecall的返回值只有1个，表示delegatecall是否调用成功的布尔变量。
在0.6.8版本的solidity中，delegatecall的返回值有2个，一个是表示delegatecall是否调用成功的布尔变量，另一个则是被调用函数的返回值。

通过delegatecall调用逻辑合约来修改数据合约中的状态变量，从而实现数据和逻辑分离。后面可以通过升级逻辑合约来改变业务逻辑，但数据合约不能升级。

下面通过例子来说明在0.6.8版本的solidity中如何使用delegatecall进行合约升级。

合约代码：

pragma solidity ^0.6.8; 


// 数据合约
contract DataContract {    

    uint256 public num1;
    uint256 public num2;
    uint256 public num3;
    address public issuer;

    
    
    event Log(string str, bool result);
    event Log2(string str, uint256 result);
    
    constructor() public {
        issuer = msg.sender;
        num1 = 1;
        num2 = 2;
        num3 = 3;
    }
    
    function callLogicContract(address logicContractAddr) public {

        bool r;
        bytes memory s;

        // 通过delegatecall调用逻辑合约来修改数据合约中的状态变量，从而实现数据和逻辑分离。后面可以通过升级逻辑合约来改变业务逻辑，但数据合约不能升级
        (r, s) = logicContractAddr.delegatecall(abi.encodeWithSignature("test(address)", this)); 
        emit Log("delegatecall return ", r);  // r为true或false
        uint256 result = bytesToUint(s);
        emit Log2("test() return ", result);
    } 

    function bytesToUint(bytes memory b) public pure returns (uint256){

        uint256 number;
        for(uint i= 0; i<b.length; i++){
            number = number + uint8(b[i])*(2**(8*(b.length-(i+1))));
        }
        return  number;
    }

    function setNum1(uint256 s) public {
        num1 = s;
    }
    
    function setNum2(uint256 s) public {
        num2 = s;
    }

    function setNum3(uint256 s) public {
        num3 = s;
    }
    
    function getNum1() public view returns(uint256){
        return num1;
    }
    
    function getNum2() public view returns(uint256){ 
        return num2;
    }
    
    function getNum3() public view returns(uint256){ 
        return num3;
    }
} 


// 升级前的逻辑合约
contract LogicContract {

    uint256 public num1;
    uint256 public num2;
    uint256 public num3; //num1, num2, num3声明的顺序和位置必须和DataContract中的一样，否则无法修改DataContract中的num3
    address public caller;
    address public dataContract;
    
    event Log(string str, uint256 num);
    event Log2(string str, address addr);
    
    function test(address addr) public returns(uint256) {
            dataContract = addr;    // 数据合约DataContract地址
            caller = msg.sender;    // 运行数据合约DataContract的以太坊账号
            num3 = num3*10; // DataContract通过delegatecall调用LogicContract的test函数，test函数里修改的是DataContract中的num3而不是LogicContract中的num3
            emit Log("after upgrading contract, num3=", num3);
            emit Log2("dataContract=", dataContract);
            emit Log2("caller=", caller);
            return num3;
    }
}


// 升级后的逻辑合约
contract LogicContract2 {

    uint256 public num1;
    uint256 public num2;
    uint256 public num3; //num1, num2, num3声明的顺序和位置必须和DataContract中的一样，否则无法修改DataContract中的num3
    address public caller;
    address public dataContract;

    
    event Log(string str, uint256 num);
    event Log2(string str, address addr);
    
    function test(address addr) public returns(uint256) {
            dataContract = addr;    // 数据合约DataContract地址
            caller = msg.sender;    // 运行数据合约DataContract的以太坊账号
            num3 = num3*300; // DataContract通过delegatecall调用LogicContract的test函数，test函数里修改的是DataContract中的num3而不是LogicContract2中的num3
            emit Log("after upgrading contract, num3=", num3);
            emit Log2("dataContract=", dataContract);
            emit Log2("caller=", caller);
            return num3;
    }
}

地址列表：

运行数据合约DataContract的以太坊账号：0xC264358Ef94b48B62e7F94ce10795255f8b9EED7
数据合约DataContract地址： 0x4ABFb9D52f63834b2A30B42202Be4F43C8CC8b48
逻辑合约LogicContract地址： 0x565d6eE58b7D0d4BbdA5e2E337eaada2D634B40D
逻辑合约LogicContract2地址： 0x9c9f6158adC9B7E9FE5fF99cEE27eECE6433edCb

运行结果的输出日志：

升级合约前，调用合约LogicContract的test函数的日志输出

logs 	[
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0xdd970dd9b5bfe707922155b058a407655cb18288b807e2216442bca8ad83d6b5",
		"event": "Log",
		"args": {
			"0": "after upgrading contract, num3=",
			"1": "30",
			"str": "after upgrading contract, num3=",
			"num": "30",
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x953bb7c6c7f939308a523ff2ce38248d9a26e7e8212c5f982fd8dffaca3fc523",
		"event": "Log2",
		"args": {
			"0": "dataContract=",
			"1": "0x4ABFb9D52f63834b2A30B42202Be4F43C8CC8b48",
			"str": "dataContract=",
			"addr": "0x4ABFb9D52f63834b2A30B42202Be4F43C8CC8b48",
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x953bb7c6c7f939308a523ff2ce38248d9a26e7e8212c5f982fd8dffaca3fc523",
		"event": "Log2",
		"args": {
			"0": "caller=",
			"1": "0xC264358Ef94b48B62e7F94ce10795255f8b9EED7",
			"str": "caller=",
			"addr": "0xC264358Ef94b48B62e7F94ce10795255f8b9EED7",
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x52dd9d08c343f72c69027ade2a075f6242dba2eeca3a3c61bfd8d00d32f6bd20",
		"event": "Log",
		"args": {
			"0": "delegatecall return ",
			"1": true,
			"str": "delegatecall return ",
			"result": true,
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x0c231cace93330e81aabd308eaecd9a98302e543efad0c88d0b99732e7c2ef5f",
		"event": "Log2",
		"args": {
			"0": "test() return ",
			"1": "30",
			"str": "test() return ",
			"result": "30",
			"length": 2
		}
	}
]

升级合约后，调用合约LogicContract2的test函数的日志输出

logs 	[
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0xdd970dd9b5bfe707922155b058a407655cb18288b807e2216442bca8ad83d6b5",
		"event": "Log",
		"args": {
			"0": "after upgrading contract, num3=",
			"1": "9000",
			"str": "after upgrading contract, num3=",
			"num": "9000",
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x953bb7c6c7f939308a523ff2ce38248d9a26e7e8212c5f982fd8dffaca3fc523",
		"event": "Log2",
		"args": {
			"0": "dataContract=",
			"1": "0x4ABFb9D52f63834b2A30B42202Be4F43C8CC8b48",
			"str": "dataContract=",
			"addr": "0x4ABFb9D52f63834b2A30B42202Be4F43C8CC8b48",
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x953bb7c6c7f939308a523ff2ce38248d9a26e7e8212c5f982fd8dffaca3fc523",
		"event": "Log2",
		"args": {
			"0": "caller=",
			"1": "0xC264358Ef94b48B62e7F94ce10795255f8b9EED7",
			"str": "caller=",
			"addr": "0xC264358Ef94b48B62e7F94ce10795255f8b9EED7",
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x52dd9d08c343f72c69027ade2a075f6242dba2eeca3a3c61bfd8d00d32f6bd20",
		"event": "Log",
		"args": {
			"0": "delegatecall return ",
			"1": true,
			"str": "delegatecall return ",
			"result": true,
			"length": 2
		}
	},
	{
		"from": "0x4abfb9d52f63834b2a30b42202be4f43c8cc8b48",
		"topic": "0x0c231cace93330e81aabd308eaecd9a98302e543efad0c88d0b99732e7c2ef5f",
		"event": "Log2",
		"args": {
			"0": "test() return ",
			"1": "9000",
			"str": "test() return ",
			"result": "9000",
			"length": 2
		}
	}
]