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1 comment by Herr_Alien on Apr 26th, 2010

If you already programmed in COM, feel free to skip the article. Yep. Nothing interesting for you here.

If you're a coder that has some experience with previous game engines but you're new to Unity, then read on.

So. Two programs and a technology for software development. And a picture:COM object and interfaces

That's a COM object. Our target is "Outer Object". It imlements several interfaces, the circles labeled A, B ...

In terms of inheritance, you could do that by deriving the class describing. Now of course, there are some problems when all them interface implement a function with the same signature, say void Update(): which Update() should be called in your case? The one from A? Or B? Or C? I personally don't like C, as a vitamin at least it is sour.

This is where COM ... comes in place. In COM, if you want to implement an interface on an object, you'll get a new instance of a class. That means that somehow, in your objects, you'll have at least three class instances, one that implements the functionality of A, one for B, well, you get the point.

Why the frowned face? Oh, stupid me, I forgot something: from now on, your object is no longer an instance of one class. No. That's gone. Think of it as a collection of classes, each working together to provide functionality for one object.

Now I can hear you saying: "But what if I need to use functionality from Interface A in the implementation of Interface B? How can I reach one functionality from the other?"

In all technologies that implement an object modeling mechanism (yep, that's the OM from COM), there will always be a mechanism to go from one interface to the other. In COM, it is called "QueryInterface". In Unity, you GetComponent.

Now it makes sense. This is why the First Person Controller prefab in Unity looks like this:

Unity's fps controller

You'll see that I underlined two components (get used to the term if you plan to use Unity). If you double click them, you'll end up looking at some C# code. Each of the scripts describe a class, each having a Start() and Update() function. Several components, working to define one object.
And here's another thing about COM: you can re-use components:


The Mouse Look script is the shared component here.

That's it. Don't say I didn't warn you, if you know COM this was not a surprise.

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Post comment Comments  (20 - 28 of 28)
KOM Jan 24 2009, 1:15pm says:

hey thanks for watching the mod

+1 vote     reply to comment
Herr_Alien Creator
Herr_Alien Jan 30 2009, 5:08am replied:

You lost me a bit :)
Anyway, I really like the game, and I do enjoy modding it. As for this particular project, it was needed.

I whish you guys good luck! I will definitely play your mod when it is released.

+1 vote   reply to comment
SinKing Oct 14 2008, 10:12am says:

I wish it would say "Seamen", instead of "Airmen" in your signature.

Nice go with releasing AvP2 Fortress, any new projects on the horizon, yet?

+1 vote     reply to comment
Herr_Alien Creator
Herr_Alien Oct 14 2008, 12:59pm replied:

Well, there is one project I'm working on. Since Sierra will pull the plug on the AvP2 master server, we're now focused in modding AvP2 to use a different and brand new master server.

That takes all my time at the moment.

On the more casual modding side, AvP2 Fortress will get some new maps, but again, developed by Windebieste. There's another guy making an interesting 1Flag-CTF map, there's a good chance of adding that one too.

+1 vote   reply to comment
Husayn-al-Musayyab Jul 17 2008, 10:09am says:

Good work in the AVP2 Fortress.

+2 votes     reply to comment
Herr_Alien Creator
Herr_Alien Jul 18 2008, 5:02pm replied:

Hey, thanks!

+1 vote   reply to comment
Arxae Jul 15 2008, 5:57am says:

srry wrong button for friends thingy :p axidentaly clicked deny -_-

+1 vote     reply to comment
Herr_Alien Creator
Herr_Alien Dec 20 2007, 3:22pm says:


Well, Ballistic 2 is a mod for AvP2. You can downlad the mod by clicking on the download link (the red button) from this page:

+1 vote   reply to comment
ShykoUzamakai Dec 18 2007, 4:38pm says:

Hey How do i Down load alien vs predator 2 please respond

+1 vote     reply to comment
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