第94篇 合约间调用（三）

1.结合法

结合前面两篇文档，将上篇的 contractC 加入接口定义，并通过接口获取函数签名；

contractD.sol

pragma solidity^0.5.0;

interface ContractInterface {
	function setRandomN(uint _limit) external returns(bool);
	function getRandomN() view external returns(uint); 
}

contract contractD {
    uint public randomN;

    function callSetRandomN(ContractInterface _contract, uint _limit) public returns(bool) {
        bytes memory _calldata = abi.encodeWithSelector(_contract.setRandomN.selector, _limit);
        (bool success, bytes memory returnData) = address(_contract).call(_calldata);
        require(success == true, "call failure");
		return abi.decode(returnData, (bool));
    }

    function callGetRandomN(ContractInterface _contract) public returns(uint) {
        bytes