Question

Requirements:

1. Section is created by selecting one teacher, one subject and one
   schedule.

2. System verifies that all business rules are followed.

   • System detects that a business rule is not being followed.

   • System informs user of conflict.

   • System doesn’t create new section.

3.System creates new section.

My problem is, if I define a constructor for section, Section(Teacher t, Subject s, Schedule c), I don’t know how to return the error message for the conflict.

Should I just let my constructor throw an exception? If yes, how to return a string from a caught exception? How to create that exception?

Or is there any better, yet simple, implementation?

Answer 1

Reporting constructor failure boils down to two options:

1. Throw an exception as you suggest. This is a reasonable approach if failure is not expected to happen often and is truly “exceptional”.
2. If failure is a normal part of the business logic, I’d recommend using the Factory pattern and returning a wrapper object that contains the newly created object plus a status variable that can indicate the detailed causes of the failure when it occurs.