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Editorial Team
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Asked: 2026-05-14T04:54:42+00:00

I have defined an Event class: Event and all the following classes inherit from

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I have defined an Event class:

Event

and all the following classes inherit from Event:

SportEventType1 SportEventType2 SportEventType3 SportEventType4

Right now I will only have SportEvents but I don’t know if in the future I’ll want some other kind of events that doesn’t even have anything to do with Sports.

Later, I will want to draw some graphics with info taken from Events, and the drawing logic can be a bit complex. But, for the moment, I think I shouldn’t think of how the drawing will be done and I believe that maybe it’d be better if that drawing part was not put as an integral part of the Event/SportEventX class chain.

I am looking for solutions for this problem. I know I could just make Event have an instance variable(attribute, for the java crowds) pointing to something as an IDrawInterface, but that would make the Event class “assume” it will be later used for drawing. I would like to make the Event class oblivious to this if possible.

Thanks!

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1 Answer

  1. Editorial Team

    Your intent to keep knowledge of the drawing process outside the Event class hierarchy is good.

    A common way to handle this sort of thing in an OO language is the Visitor Pattern.

    If you can’t actually change the Event class to add the accept(Visitor v) needed for Visitor, you might consider using a Decorator or an Adapter. Getting the accept method to vary by subclass might be painful with these though. I’ll think about this a bit more and maybe add further notes tonight. For now, I’ve got to get to work.

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