ContractCallContract

pragma solidity 0.6.2;

/*
    合约调用合约，并解析返回参数
*/
contract ContractCallContract{

    event Call(bytes k1,uint256 k2,uint256 k3);

    function callContractByEncodeWithSelector(address contractAddress,uint256 a,uint256 b) public {
        (bool success, bytes memory data) = contractAddress.call(abi.encodeWithSelector(getSelector(),a,b));
        require(success,"call A is fail");
        (uint256 c,uint256 d) = abi.decode(data,(uint256,uint256));
        emit Call(data,c,d);
    }

    function callContractByEncodeWithSignature(address contractAddress,uint256 a,uint256 b) public {
        (bool success, bytes memory data) = contractAddress.call(abi.encodeWithSignature("add(uint256,uint256)",a,b));
        require(success,"call A is fail");
        // 解析data
        (uint256 c,uint256 d) = abi.decode(data,(uint256,uint256));
        emit Call(data,c,d);
    }

    function callA(bytes4 b4,uint256[] memory list,address contractAddress) public {
        (bool success, bytes memory data) = contractAddress.call(abi.encodeWithSelector(b4,list));
        require(success,"call A is fail");
        // 解析data
        (uint256 a,uint256 b) = abi.decode(data,(uint256,uint256));
        emit Call(data,a,b);
    }

    function getSelector() public pure returns(bytes4){
        return bytes4(keccak256(bytes('add(uint256,uint256)')));
    }

    function getAddSelector() public pure returns(bytes4){
        return bytes4(keccak256(bytes('add(uint256[])')));
    }



}

contract A{
    function add(uint256 a,uint256 b) public pure returns(uint256,uint256){
        return (a+b,a-b);
    }
    function add(uint256[] memory a) public pure returns(uint256,uint256){
        return (a[0]+a[1],a[0]-a[1]);
    }
}