The code described seems to result in a scenario where...

The code described seems to result in a scenario where a guard is assigned to multiple gates in the database. Based on your description, it appears this behavior violates the business rule that a guard should only be assigned to one gate at a time.

What the code does:

1. Initially, you assign a guard to a gate.
2. Later, you assign the same guard to a different gate.
3. Instead of updating the existing record in the database to reflect the new assignment (guard to the new gate), the code inserts a new record, leaving the original assignment intact. Therefore, the guard becomes assigned to two gates simultaneously.

The problem:

The issue arises because the database or application logic:

• Fails to enforce a constraint ensuring that a guard can only exist in a single gate assignment at a time.
• Does not check whether the guard is already assigned to a gate before inserting or saving another assignment.

How to fix the issue:

1. Database Constraints: Add a unique constraint in the database to ensure that each guard can only have one active gate assignment at a time.
   • Example schema fix: Add a Unique constraint on the guard_id column in the table that stores the assignments.
2. Application Logic: Modify the code to:
   • Check if the guard is already assigned to a gate before assigning them to a new one.
   • If an assignment exists, update the existing record instead of creating a new one.

Summary:

The code in its current form inserts new records for gate assignments without checking if the guard has an existing assignment, causing the guard to be assigned to multiple gates simultaneously, which conflicts with the expected rule.