Solidity contract call contract

BaseExtra.sol

/// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

// Adapted from https://ethereum.stackexchange.com/questions/45277/calling-one-contract-to-another-contract-method

contract Base {

    uint public dataA;
    bytes4 public dataB;

    function setAB(uint a, bytes4 b) public {
        dataA = a;
        dataB = b;
    }

    function getA() public view returns(uint) {
        return dataA ;
    }

    function getB() public view returns(bytes4) {
        return dataB ;
    }

}

contract Extra {

   Base base;

   function Extra() public {
       base = new Base();
   }

   function getBaseAddres() public view returns(address) {
       return address(base);
   }

   function baseGetA() public view returns(uint) {
        return base.getA();
   }

   function baseGetB() public view returns(bytes4) {
       return base.getB();
   }

   function baseSetAB(uint a, bytes4 b) public returns(bool success) {
       base.setAB(a,b);
       return true;
   }
}