I’ve got a class called List_Field that, as the name suggests, builds list input fields. These list input fields allow users to select a single item per list.
I want to be able to build list input fields that would allow users to select multiple items per list, so I have the following dilemma:
Should I do that through implementing a multiple_choice_allowed property into the existing List_Field property, or should I implement a Multiple_Choice_List_Field subclass of the List_Field class?
What’s the engineering principle that I should follow when confronted with dilemmas like this one?
Take a look at the SOLID principles. They’ll help you in your designs. In particular, the single responsibility principle will tell you not to mix the two concerns in one class, and the Liskov substitution principle will tell you not to create subclasses that break the contract of superclasses, like what you’re also proposing.
So what would be the solution in your case? You could create an abstract base class that would be agnostic to the type of selection and then create 2 subclasses, one for single selection and another for multiple selection.