I'm trying to figure out the best design here, and I can see multiple approaches, but none that seems "right."

There are three relevant classes here: Base, TradingPost, and Resource. Each Base has a TradingPost which can offer various Resources depending on the Base's tech level.

Where is the right place to store the minimum tech level a base must possess to offer any given resource? A database seems like overkill. Putting it in each subclass of Resource seems wrong--that's not an intrinsic property of the Resource. Do I have a mediating class, and if so, how does it work? It's important that I not be duplicating code; that I have one place where I set the required tech level for a given item. Essentially, where does this data belong?

P.S. Feel free to change the title; I struggled to come up with one that fits.

  • 1
    \$\begingroup\$ It sounds like you can just keep this as an attribute of the base: a list of resources, and a correlating list of the minimal base level before that resource appears. \$\endgroup\$
    – ashes999
    Commented Jan 3, 2013 at 16:20

1 Answer 1


IMHO, the responsibility of managing which Resources are available in a TradingPost should be in a separate controller-like class, TradingPostController for example.

TradingPostController observes changes of Base.techLevel and updates the TradingPost's set of offered Resources accordingly. In this approach, TradingPostController will contain a mapping of tech level -> resource set.

So the sequence of events would be:

  • Tech-level of Base is increased.
  • Base fires a "tech level changed" event.
  • TradingPostController observes the event.
  • TradingPostController updates TradingPost.resources (or so).

Good luck!


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