05 - World Reset

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Reset world state while keeping systems registered. Useful for game restarts and state management.

Prerequisites

  • .NET SDK 8.0+ or Unity 2021.3+
  • ZenECS Core package installed
  • Understanding of World Reset

Run It

.NET Standalone

cd Packages/com.zenecs.core/Samples~/05-WorldReset
dotnet run

Unity

  1. Open Unity project
  2. Open scene: Packages/com.zenecs.core/Samples~/05-WorldReset/Scene.unity
  3. Press Play

Code Walkthrough

World Reset

Reset clears all entities and components but keeps systems:

// Setup world with systems
var world = kernel.CreateWorld(null, "GameWorld");
world.AddSystems([new MovementSystem(), new HealthSystem()]);

// Create entities
Entity player;
using (var cmd = world.BeginWrite())
{
    player = cmd.CreateEntity();
    cmd.AddComponent(player, new Position(0, 0));
}

// Reset world (entities destroyed, systems remain)
world.Reset();

// Systems are still registered
// Ready for new simulation

Complete Example

using ZenECS.Core;
using ZenECS.Core.Systems;

[FixedGroup]
public sealed class GameSystem : ISystem
{
    public void Run(IWorld world, float deltaTime)
    {
        // Game logic
    }
}

// Setup
var kernel = new Kernel();
var world = kernel.CreateWorld(null, "GameWorld");
world.AddSystems([new GameSystem()]);

// Game loop
bool gameRunning = true;
while (gameRunning)
{
    // Run simulation
    kernel.PumpAndLateFrame(dt, fixedDelta, maxSubStepsPerFrame: 4);
    
    // Check for reset
    if (ShouldReset())
    {
        world.Reset();  // Clear entities, keep systems
        InitializeGame(world);  // Recreate entities
    }
}

// Cleanup
kernel.Dispose();

Use Cases

Game Restart

public void RestartGame()
{
    // Reset world (clears all entities)
    world.Reset();
    
    // Reinitialize game state
    Entity player;
    using (var cmd = world.BeginWrite())
    {
        player = cmd.CreateEntity();
        cmd.AddComponent(player, new Position(0, 0));
        cmd.AddComponent(player, new Health(100, 100));
    }
}

Level Transition

public void LoadLevel(int levelIndex)
{
    // Reset current level
    world.Reset();
    
    // Load new level entities
    LoadLevelEntities(world, levelIndex);
}

Best Practices

✅ Do

  • Use for restarts: Fast way to reset state
  • Keep systems: Systems remain registered
  • Reinitialize: Recreate entities after reset
  • Test thoroughly: Verify reset works correctly

❌ Don't

  • Don't reset during iteration: Reset at safe boundaries
  • Don't forget to reinitialize: Entities are cleared
  • Don't reset unnecessarily: Only when needed

See Also

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