Proxy Contract Not Updating Store Data

Question

I want to setup a proxy contract that my users can interact with. The proxy contract is a store contract with stores the user's age for now. When I call writeData to update my age, I expect it to call my logic contract to run the update there.

When I run the code below in Remix, I am unable to update the userData mapping. When I enter an age of 30, it returns 0 for BOTH contracts so I assume the call is failing. However, if I call writeData on the logic contract, it writes just fine. I assume there is something wrong with my delegatecall.

I am following https://blog.trailofbits.com/2018/09/05/contract-upgrade-anti-patterns/ (under Delegatecall-based proxy pattern ) and I have my state variables ordered correctly so I don't expect it to write to my proxy address by accident.

What am I doing wrong here?

Storage/Proxy Contract:

pragma solidity ^0.4.23;

// Storage contract
contract HealthcareStorage  {

  mapping (address => uint8) public userData;

  address public logicContract;
  address public owner;

  constructor(address _logicContract) public {
    logicContract = _logicContract;
    owner = msg.sender;
  }

  function updateContract(address _newAddress) public returns (bool) {
    require(msg.sender == owner);
    logicContract = _newAddress;

    return true;
  }

  function writeData(uint8 _age) public {
   logicContract.delegatecall(bytes4(keccak256("writeData(uint8)",_age)));
  }
}

Logic Contract:

pragma solidity ^0.4.23;

import { HealthcareStorage } from "./HealthcareStorage.sol";

// Logic contract - Upgradeable
contract HealthcareLogic{

  mapping (address => uint8) public userData;


  function writeData(uint8 _age) public returns (bool) {
    userData[msg.sender] = _age;

    return true;
  }

}

Answer 1

Turns out this line was off:

logicContract.delegatecall(bytes4(keccak256("writeData(uint8)",_age)));

It should be:

logicContract.delegatecall(bytes4(keccak256("writeData(uint8)")),_age);