Object-oriented Modeling & Design, Assignment IV.
Gang of Four (GoF) design patterns etc.
From the behavioral aspect, GPA and student are different kinds. A student does not have to have a GPA, at all. For instance, a student might be enrolled to a course without a grading system. Hence, the contract cannot be provided by all possible concrete implementations of an abstract student implementation containing abstract method(s) for calculating GPA.
The solution for the problem could be implementing a grading calculation strategy, which is contained by a Student object.
In overall, we prefer composition over inheritance, since the calculation of GPA should be seperated from the logic of Student class' itself.
If there is a GPA to be calculated, how to calculate it must be decided during creation of the Student object.
A factory class for creating GpaStrategy objects can be implemented.
The new factory class can implement a factory method with a year parameter to provide objects to various Students.
The system is highly cohesive, since the responsibility of creating strategy objects is now at factory class.
Instead of implementing new class for each GPA calculation method, we could implement a parametric class which makes a general implementation.
The Grade object may contain score and weight properties to supply enough information to the GPA calculator algorithm.
Most of the time, GPAs will be calculated with a Grade object.
One could implement such class, who is responsible for calculating GPA, with parameters of minimum and maximum boundaries of the grading system.
For example, instead of having classes for each GPA calculation method, we could parameterize the function.
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