⚛️ P-E-R-R-Y ECS

A modern, lightweight Entity-Component-System framework in C++.

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✨ Overview

P-E-R-R-Y ECS is a header-only, type-safe library for game development, simulations, or any system that benefits from separating data from logic.

It implements the Entity-Component-System (ECS) pattern with modern C++ features:

• Templates & variadic functions for type safety
• Optional concepts (C++20) for system constraints
• Efficient storage and fast iteration

Core goals:

• 🧩 Component-oriented storage with type-safety
• ⚡ Fast lookups via SparseArray and type-based storage
  
• 🔄 Flexible Systems: can operate on any combination of components
• ✅ Unit-tested with GoogleTest
  
• 🚀 Header-only, easy integration

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🧱 Features

• Create entities and attach any combination of components
  
• Add systems that operate on specific components
  
• Variadic interface: add multiple components or systems at once
  
• Owned (rvalue) vs Non-owned (lvalue) systems
  
• Safe runtime updates via Registry::callSystem<System>()
  
• Component access via getComponents<T>()
  

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🧩 Example Usage

#include "Ecs.hpp"
#include <memory>
 
using namespace ecs;
 
struct Velocity { int x, y; };
struct Position { int x, y; void operator+=(const Velocity& vel) { x += vel.x; y += vel.y; } };
struct Health { int value; };
 
// --- Systems ---
class MoveSystem: public ISystem {
    public:
        MoveSystem() {}
 
        void update(Registry &r) override {
            auto& positions = r.getComponents<Position>();
            auto& velocities = r.getComponents<Velocity>();
 
            for(size_t i = 0; i < positions.size(); ++i) {
                if (positions[i] && velocities[i])
                    positions[i].value() += velocities[i].value();
            }
        }
};
 
int main() {
    Registry registry;
 
    using MyComponents = std::tuple<Position, Velocity, Health /*, ...*/>;
    registry.registerComponentsByExtraction<MyComponents>(); 
    //or use registry.registerComponents<Position /*, ...*/>();
 
    Entity player = registry.createEntity();
    Entity enemy = registry.createEntity();
 
    Health h{100}; 
 
    player.addComponent(Position{0, 0}, Velocity{1, 0}, h /*, ...*/);
    registry.addComponent(enemy, Health{50} /*, ...*/);
 
    auto&positons = registry.getComponents<Position>();
 
    registry.addSystem(MoveSystem()/*, ...*/);
 
    registry.callSystem<MoveSystem/*, ...*/>();
}