CODEWITHSUNDEEP
c++c++11templatescomponentsentity-component-system
user3097902
user3097902

Reputation: 25

c++ entity component system and accessing components using a template

I've been working on creating my own entity component system, and I'm set on being able to get a component by doing the following:

const auto& component = entity->GetComponent<ComponentType>();

The above function would then look something like this:

template <typename TyComponent>
TyComponent* Entity<T>::GetComponent() const
{
  return &(GetComponent(TyComponent::Id());
}

Which then returns a component based on the associated id if found, else nullptr.

  1. Is what I'm doing viable?
  2. Is there a way to ensure only types derived from Component can be used as a parameter for GetComponent?

Upvotes: 2

Views: 1657

Answers (1)

Michael Anderson
Michael Anderson

Reputation: 73590

This design is OK.

You'll already get a compile time error if anyone tries GetComponent<Foo>, but Foo doesn't have a static Id() function. So that gives you a bit of safety.

However, it still needs one change to compile. Here's how I'd do it:

Component * GetComponent(int id) { ... }

template <typename TyComponent>
TyComponent* Entity<T>::GetComponent() const {
  return dynamic_cast<TyComponent*>(GetComponent(TyComponent::Id()));
}

This will now generate a compile error when TyComponent is not derived from Component. (Component will need at least one virtual function for this to work though.)

Upvotes: 2

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