Entity Queries

[doonv]

Currently, you cannot access entities properties. In order to access entities properties we will need entity queries. Entity queries will be a built-in parser feature that will allow you to query the entities you choose and modify them.

Design

Todo list for the design of the entity queries.

• [ ] Design the syntax.
  • [ ] Id queries
  • This should probably be just the entity id, very simple.
  • [ ] Single queries
  • Queries for a single entity and provides access to all of their components.
  • [ ] For-each queries
  • Queries for a group of entities based on their components and executes a command on each of them.
• [ ] Figure out how to create dynamic reflection-based queries at runtime.

Implementation

After the design has been finished, we can start the implementation.

• [ ] Parsing
  • [ ] Id Queries
  • [ ] Single queries
  • [ ] For-each queries
• [ ] Execution
  • [ ] Id Queries
  • [ ] Single queries
  • [ ] For-each queries

[nicopap]

I've designed a DSL for querying here https://github.com/nicopap/bevy_mod_dynamic_query/tree/main/examples/query_interpreter#query-grammar if you need some inspiration. You can always re-use the bevy type DSL though.

[doonv]

That looks cool, How will I go from the regular built-in parser to the DSL though?

[nicopap]

I mean, you write a grammar that supports the rust syntax. The full parser for both syntax is defined here https://github.com/nicopap/bevy_mod_dynamic_query/blob/149b5d4a5a3611373b99b83bc9075cbd7d03b01e/examples/query_interpreter/src/query_parser.rs. Similarly to video game FX, no need to support all the intricacies of the rust syntax, it just need to look like it :P

[doonv]

I meant something like $( insert query here ).MyProperty = 5.4. The $( ... ) transitions from the built-in parser's language to the Querying DSL. I kinda like the $( ... ) syntax what do you think?

[nicopap]

Always can use a keyword that it a rust keyword, so that you are sure to avoid overlapping with pre-existing field names. For example for ( bindings ) in <query> { … }. Or terser yet: for(<query>).… (yield?). I also like the functional style, swapping for with map.

[doonv]

@nicopap I'd like to use your bevy_mod_dynamic_query library for this, and I have a few issues with it. but it looks like issues are disabled. Can you re-enable them?

[nicopap]

Issues are now re-enabled on bevy_mod_dynamic_query.

[doonv]

Thanks!

[doonv]

Ah turns out my issue is actually not a problem.

[doonv]

This is currently blocked by either of the following:

• bevy_mod_dynamic_query isnt updated for Bevy 0.12.
• Bevy 0.13 has dynamic querying, but it isn't released yet.