EasyS is a minimalist, header-only C++ library designed to streamline the development of applications using the Entity Component System (ECS) architecture. With a focus on simplicity, flexibility, and ease of use, it offers developers an unopinionated foundation to build efficient, high-performance systems without the overhead of external dependencies.
The library uses a static design approach, requiring all component types to be registered at compile time through template parameters.

Easys::ECS

The Easys::ECS class is the single public interface for EasyS. It provides all functionality for:

Compile-time component registration
Entity creation and management
Component addition, removal, and querying

All public operations are available as member functions. See the API Reference for a complete list and descriptions.

Quick Start Guide

This basic example demonstrates how to create entities, add components, and retrieve them:

#include <easys/easys.hpp>
#include <iostream>
 
// This is a very basic example to demonstrate creating an entity,
// adding a component to it, and retrieving the component.
 
// Define a Position component structure.
// Components are simple structs or classes that contain data.
struct Position {
    float x, y;
};
 
int main()
{
    using namespace Easys;
  
    // Create an instance of the ECS class and register all component types.
    ECS<Position> ecs;
 
    // Create a new entity. An entity is just a number.
    Entity entity = ecs.addEntity();
 
    // Add a Position component to the entity with initial values.
    ecs.addComponent<Position>(entity, {10.0f, 20.0f});
 
    // Update the component.
    auto &component = ecs.getComponent<Position>(entity);
    component.x = 0.0f;
 
    // Retrieve the Position component from the entity to read or modify it.
    Position &pos = ecs.getComponent<Position>(entity);
    std::cout << "Position: " << pos.x << ", " << pos.y << std::endl;
 
    return 0;
}

Note: For more usage examples, take a look at the examples.

Configuration Options

EasyS provides a couple of overrideable macros to tailor the ECS to your use case:

EASYS_ENTITY_TYPE - define the integer type used for entity IDs (default: uint32_t)
EASYS_ENTITY_LIMIT - set the maximum number of active entities (default: 10000)

Define these macros before including EasyS, either in source or via compiler flags.

Customizing in Source Code

#define EASYS_ENTITY_TYPE uint64_t // Change to 64-bit unsigned integer
#define EASYS_ENTITY_LIMIT 50000   // Increase entity limit
#include <easys/easys.hpp>         // Path to the configuration file

Customizing with Compiler Flags

GCC/Clang on Linux/macOS:

g++ -DEASYS_ENTITY_TYPE=uint64_t -DEASYS_ENTITY_LIMIT=50000 -o my_app my_app.cpp

MSVC on Windows:

cl /D EASYS_ENTITY_TYPE=uint64_t /D EASYS_ENTITY_LIMIT=50000 my_app.cpp

Depending on your compiler and development environment the exact command might be slightly different.

Philosophy and User Responsibilities

Note

Users are expected to:

Register all Components at Compile-Time: All component types must be specified as template parameters when instantiating the ECS. Accessing a foreign component will result in a compiler error.
Check Component Presence Before Access: Always verify that an entity has a given component before accessing it. Calling Easys::ECS::getComponent<T>(entity) on an entity that lacks T will throw a Easys::KeyNotFoundException.