Get userID and save it in function - Solidity Beginner - solidity

Question

This is my first Solidity project.
I'm trying to create a kind of supply chain, more than anything just practice code.
I came across a problem that I couldn't solve or find the solution online.
Problem: I want to get the user ID and save it in each function so it would look like...
function Customer() public {
checked = Process.Received;
status = Process.NotPaid;
//userid = Process.< THE ID >
}
I tried with this ...
function getStruct() public
view
returns (string, uint)
{
return (User);
}
But keeps on asking me to have the data located in memory. Which I tried but won't work for me.
Full code:
pragma solidity ^0.5.1;
contract SupplyChain {
enum Process {
Unknown,
Checked,
Received,
Paid,
NotPaid
}
Process public status;
Process public checked;
Process public userid;
address user;
struct User {
uint _id;
string _firstName;
string _lastName;
}
constructor() public {
status = Process.Unknown;
user = tx.origin;
}
function addUser(
uint256 id,
string memory _firstName,
string memory _lastName
) public{
}
// NOT FINISHED NEED TO RETURN USER ID TO PRINT IN TRACKERS.
function getStruct() public
view
returns (string, uint)
{
return (User);
}
function Factory() public {
checked = Process.Checked;
status = Process.NotPaid;
// print userid
}
function TransportOne() public {
checked = Process.Checked;
status = Process.NotPaid;
// print userid
}
function Deposit() public {
checked = Process.Checked;
status = Process.NotPaid;
// print userid
}
function TransportTwo() public {
checked = Process.Checked;
status = Process.NotPaid;
// print userid
}
function Customer() public {
checked = Process.Received;
status = Process.NotPaid;
// print userid
}
}

Answer 1

There is no print in solidity, you can try to use events for logging.
If you just want to debug, you can try Remix IDE.