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94 lines
2.8 KiB
Markdown
94 lines
2.8 KiB
Markdown
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# Frequently Asked Questions
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This section addresses common questions about jecs.
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## General Questions
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### What is jecs?
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jecs is a high-performance Entity Component System (ECS) library for Luau/Roblox.
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### How does jecs compare to other ECS libraries?
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jecs uses an archetype-based storage system (SoA) which is more cache-friendly than traditional approaches. For a detailed comparison with Matter, see the [Migration from Matter](../migration-from-matter.md) guide.
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### Can I use jecs outside of Roblox?
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Yes, jecs can be used in any Lua/Luau environment as it has zero dependencies.
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## Technical Questions
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### How many entities can jecs handle?
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jecs can handle up to 800,000 entities at 60 frames per second.
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### What are archetypes?
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Archetypes are groups of entities that have the exact same set of components. When you add or remove components from an entity, it moves to a different archetype.
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### How do I optimize performance with jecs?
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- Group entity operations to minimize archetype transitions
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- Use cached queries for frequently accessed data
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- Define components that are frequently queried together
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- Use tags instead of empty tables
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- Be mindful of archetype transitions
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### What are relationship pairs?
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Relationship pairs allow you to create connections between entities using the `pair()` function.
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## Common Issues
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### My entity disappeared after adding a component
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Check if you have cleanup policies set up with `OnDelete` or `OnDeleteTarget`.
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### Queries are returning unexpected results
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Make sure you're querying for the exact components you need. Use modifiers like `.with()` or `.without()` to refine queries.
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### Performance degrades over time
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This could be due to:
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- Memory leaks from not properly deleting entities
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- Excessive archetype transitions
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- Too many entities or components
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- Inefficient queries
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### How do I debug entity relationships?
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Use the `Name` component to give entities meaningful names:
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```lua
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-- Print all parent-child relationships
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for entity, target in world:query(jecs.pair(jecs.ChildOf, jecs.Wildcard)) do
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print(world:get(entity, jecs.Name), "is a child of", world:get(target, jecs.Name))
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end
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```
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## Best Practices
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### When should I use component lifecycle hooks?
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Use lifecycle hooks (`OnAdd`, `OnRemove`, `OnSet`) for:
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- Initializing resources
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- Cleaning up resources
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- Reacting to data changes
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### How should I structure my ECS code?
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- Separate data (components) from behavior (systems)
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- Keep components small and focused
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- Design systems for specific component combinations
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- Use relationships to model connections
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- Document cleanup policies
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### Should I use multiple worlds?
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Multiple worlds are useful for:
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- Separating client and server logic
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- Creating isolated test environments
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- Managing different game states
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Component IDs may conflict between worlds if not registered in the same order.
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