How should I plan the inheritance structure for my game?
Posted
by
Eric Thoma
on Game Development
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Published on 2012-12-16T01:33:23Z
Indexed on
2012/12/16
5:20 UTC
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I am trying to write a platform shooter in C++ with a really good class structure for robustness. The game itself is secondary; it is the learning process of writing it that is primary.
I am implementing an inheritance tree for all of the objects in my game, but I find myself unsure on some decisions.
One specific issue that it bugging me is this:
I have an Actor
that is simply defined as anything in the game world. Under Actor
is Character
. Both of these classes are abstract.
Under Character
is the Philosopher
, who is the main character that the user commands. Also under Character
is NPC
, which uses an AI module with stock routines for friendly, enemy and (maybe) neutral alignments.
So under NPC
I want to have three subclasses: FriendlyNPC
, EnemyNPC
and NeutralNPC
. These classes are not abstract, and will often be subclassed in order to make different types of NPC's, like Engineer
, Scientist
and the most evil Programmer
.
Still, if I want to implement a generic NPC named Kevin, it would nice to be able to put him in without making a new class for him. I could just instantiate a FriendlyNPC
and pass some values for the AI machine and for the dialogue; that would be ideal.
But what if Kevin is the one benevolent Programmer
in the whole world? Now we must make a class for him (but what should it be called?). Now we have a character that should inherit from Programmer
(as Kevin has all the same abilities but just uses the friendly AI functions) but also should inherit from FriendlyNPC
.
Programmer
and FriendlyNPC
branched away from each other on the inheritance tree, so inheriting from both of them would have conflicts, because some of the same functions have been implemented in different ways on the two of them.
1) Is there a better way to order these classes to avoid these conflicts? Having three subclasses; Friendly
, Enemy
and Neutral
; from each type of NPC; Engineer
, Scientist
, and Programmer
; would amount to a huge number of classes.
I would share specific implementation details, but I am writing the game slowly, piece by piece, and so I haven't implemented past Character
yet.
2) Is there a place where I can learn these programming paradigms? I am already trying to take advantage of some good design patterns, like MVC architecture and Mediator objects. The whole point of this project is to write something in good style.
It is difficult to tell what should become a subclass and what should become a state (i.e. Friendly boolean v. Friendly class). Having many states slows down code with if
statements and makes classes long and unwieldy. On the other hand, having a class for everything isn't practical. 3) Are there good rules of thumb or resources to learn more about this?
4) Finally, where does templating come in to this? How should I coordinate templates into my class structure? I have never actually taken advantage of templating honestly, but I hear that it increases modularity, which means good code.
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