Remix Error: This contract does not implement all functions and thus cannot be created when trying to pass modifiers

Question

In the below code I can successfully deploy the "UserRegistry" contract, but when I try to deploy the "User" contract, I get the error This contract does not implement all functions and thus cannot be created. Based on this example, I thought I could inherit modifiers from a contract containing only modifiers. I am not seeing why I can compile this Reddit user's code but not mine as it seems to fit the same pattern.

    pragma solidity ^0.4.19;
contract UserRegistry {

    address owner;

    struct user {
        uint dateAdded;
        uint repuation;
    }

    mapping(address => user) users;

    modifier IsUser(address account) {
        require(
            users[account].dateAdded != 0   
        );
        _;
    }

    modifier OwnerApproved() {
        require(
            msg.sender == owner
        );
        _;
    }

     constructor(address _owner) public {
        owner = _owner;
    }
}

contract User is UserRegistry {

    event EventAddUser(address account);

    function addUser(address account) public {
        users[account].dateAdded = now;

        emit EventAddUser(account);
    }

    function updateUserRep(address _user) public IsUser(_user) OwnerApproved {
        users[_user].repuation +=  1;
    }

}

Answer 1

Your User class is not implementing the constructor. You can call the parent constructor in this way

constructor(address _owner) UserRegistry(_owner) public { }

please note that also the addUser is actually wrong. You need to create the struct

users[account] = user(now, 0);