Componet based entity system.

[wildrj]

Ive been reading around for about 3 days now and i just cant seem to grasp the entire idea or how id lay this type of structure out. I am currently using the traditional deep hierarchy system but its becoming a pain to further extend. Now Ive come across two systems but i don't think there fully correctly.

First one uses templates.

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HealthComponetTemplate testtemplate = new HealthComponetTemplate("testTemplate");
HealthComponet test = new HealthComponet();
test.setIntialHealth(test::leg , 100);
testtemplate.setComponet(test);

entity.setComponet(entitymanager.getTemplate("testTemplate").object);

The second system is just setting componets manually.

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HealthComponet test = new HealthComponet();
entity.setComponet(test);

The issue is if i want the entity to iterate through the list and call certain functions i cant "auto" cast so to say.

Now from what i understand is what id do is use the entity itself and use the attached componets functions.

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if(entity.getComponet(test).type == "healthComponet"){
((HealthComponet*)entity.getComponet(test))->setHealth(0);
}

Am i correct or is there something im missing?

[sudi]

Actually the casting stuff is bad!
bc that way u kinda kill the flexibility of the component system.
i would recomend a signal/slot system.
To do that your entity needs a map of signals like.

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class Entity
{
public:
          //Stuff
          irr::core::map<irr::core::stringc, Signal> Events;
          void SendEvent(const irr::c8* type, void* data);
};

Now each component registers With the entity events its functions for exaple the health component registers a event called "setHealth".
now if u want to set the health u call.

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int health = 50;
myEntity->SendEvent("setHealth", (void*)&health);

that will call all functions of components or anything else that registered to the entity. that way u need no casting or anything and it even works when the entity has no element with a setHealth function. its simply not responding then.

[ZCCdark203]

I agree with Sudi. If you're going to use a component-based entity system, it's certainly a good idea to also integrate a signal/slot system.

I use it in Sirrf. Although, in a slightly different way than Sudi described. Sirrf, for example, does use casting. The sigslot system is primarily being used for communication between entities and components.

But regardless of the way you're going to use such signal/slot system, it's a nice addition.

[wildrj]

Alright signal slot is simple enough now how to implment "get"functions
such as getHealth()... boggles me.

[bitplane]

The method takes a non-const pointer to void, you can use it for input and output: cast to the appropriate type and write to the variable.

[Dorth]

No, no, take sigslot over that implementation. It's cleaner, multithread safe and type safe.

But to get stuff, you make a signature just the same way as if you had to return an error code. Except the return value is void for reasons explained in the documentation. So:

void Func (int& ValueToRetrieve, int* OrOtherWayToRetrieve, bool SomeArg);

[sudi]

why do u want to "get" health?

[vitek]

For display in the UI perhaps?

[wildrj]

Yes for ui among other things.

[sudi]

so u could make ur health component make fire a "updateHealth" event and the ui registers for that event. that way u don't need GET methods.