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Examples of component design in simple game such as pong

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Hi Guys n Girls,

First of all i am not asking for a detailed coded example i dont care about the specific language or graphics although if you do want to type semi c++ then i could probably understand it a little faster :)

I wouldnt say im dumb but i have been having a bit of trouble grasping the component based code and i think it would help me if you could show me how you would implement this in a simple game like pong or something else quite simple.

How i understand components is that say i have classes cMove, cDraw, cCollision ect i then have an cEntity object which takes a pointer to each component i need it to have.

so maybe

class cEntity
{
cPosition* coords;
cMove* mover;
cDraw* drawer;
cCollision* collider;
}


now whether that is right or wrong im not sure but after that i am stuck as to how to implement it do i simply make a container of components and fill it from each type of different cEntity i have so i could end up with.



// these are the walls names

componentArray[0] = topWall.cPosition;
componentArray[1] = bottomWall.cPosition;
componentArray[2] = leftWall.cPosition;
componentArray[3] = rightWall.cPosition;
// and then maybe

for (int i = 0; i < totalcomponents; i++)
{
componentArray->whereIsMyPosition();
}


now please dont judge my code style i know it may be difficult to read but it is purley for an example im just wondering if i am on the right track or if i am not could you please show me with a similar example.

Many Thanks in advance :)

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Hi Guys

i would like to re-phrase my question into an actual question.

#1 do you have any example of a simplest version of a component system in the context of an actual game?

i have looked on google and only really seem to find snippets which i dont fully follow.

#2 based on my first post am i in the right ball park in terms of how i percieve component based design?

#3 do you know any good books or web pages aimed at idiots like me who cannot grasp the concept fully or ones that implement them into a working program.

many thanks you help and wisdom is much appreciated :)

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Hi,

I can't give you an answer which suits for every situation but how about making a abstract EntityComponent class from which all the components herite? You may store the components in a vector or list such as std::vector<EntityComponent *> Components; So this allows you to add and remove components easily to your entities.

Your entity should have some kind of messaging system for the components, in a way that any component can send messages to the entity itself or other components.

Is there a specific problem you are trying to solve currently?

Cheers!

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hi Kauna

thanks for your reply. im really just trying to understand how i would go about using a component system. the problem is i am struggling to find good examples and the ones i do find are a bit complex im sure i half understand it but not quite how to implement it and seeing as pong is a very simple game i figured it would only need a few components and it would be easy to see how it works.

so really its just how does component design work and how do i start to make one.

my above post isnt an example of my design rather a template to use to show me what component design really is.

thanks again for your help

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Hi FLeBlanc,

All i can say is wow!! or perhaps thank you very much :) i think i will need to re read your reply a few times but that is exactly what i needed.

the reason i said pong is because it is a simple game and i have made a version using inheritance but i have been intruiged by components and now i think im really beginning to grasp it. i could see the power of it before but not how to implement it. lots of phrases in your reply i will need to google but this is more than enough for me to get started on designing a component type game :)


well thanks again this has been an amazing response i appreciate your time and effort :)

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thank you so much that was a very kind thing to do the first post was more than enough but the second one is truely amazing smile.png
i think i understand exactly how this works now and will be studing this tread for a while but now i have the tools and the theory to move away from inheritance and focus on components smile.png

i have looked on google for this kind of example one that is simple enough to understand but shows exactly what is going on i just hope it will help future noobs like me well i know it will.

thank you for helping me smile.png



edit:
i have never used Lua and i have been reading a little to try to understand your code it seems like an awesome language i am going to test your code and then try to convert it to c++ but i think i may try to learn Lua one day :)

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Lua, as a higher-level language than C++, offers some little tricks that make things like this easier. For one, the dynamic typing means that I can easily just pass a generic table as the argument to object:message(), and leave it up to the message sender and receiver as far as the actual layout of the table, without having to resort to any of the weird templating tricks or std::map trickery I might have to use to implement a similar structure in C++. Although it's actually not too hard to do. You can use an std::map<std::string, std::string> as a quick hack, and "cast" the second string to whatever you need it to be (number, letter, string, etc...). Another bonus of developing in Lua is the ad hoc nature of prototyping and data structuring. If I am prototyping a system, I can quickly iterate on table layouts to get the data and structure I need without recompiling. Quite often I will prototype even performance-critical systems in Lua, only translating them to C++ and writing a binding layer if it happens that I need the performance.

Lua's powers for data-description also mean that I have done away with all of the special-case data file formats I once-upon-a-time came up with; you know, all the little formats for describing an animated entity, for saving level data, etc... If I have a table full of data, I can just save or load it as a compiled Lua chunk. As an example, in the above Pong demo, you could very quickly save the state of the game at any time by dumping the componentlist tables of the sub-systems to binary chunks; the state could be restored just as easily by loading the chunks back into componentlist.

These days, I write all of my "upper level" logic in Lua, and use C++ only for the performance critical stuff: rendering scene structure, physics, etc...

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Cor i know one thing Lua is a bit complicated to understand ive read a few basic love2d tutorials and i still struggling to translate your code :)

also i tried to run your script but i must be doing something wrong as it says no code to run, any ideas?

Many Thanks again :)

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