Conditional Commands

Implements three extension traits

• ConditionalInsertComponentsExt for EntityCommands and EntityMut
  with methods:
  • insert_if
  • insert_if_else
  • insert_bundle_if
  • insert_bundle_if_else
  • insert_some
  • insert_some_or_else
  • insert_bundle_some
  • insert_bundle_some_or_else
• ConditionalChildBuilderExt for EntityCommands
  with method:
  • with_children_if
• ConditionalWorldChildBuilderExt for EntityMut
  with method:
  • with_children_if

that allow for conditional component, bundle, and child insertion without the need for an intermediate EntityCommands or EntityMut binding.

• Supports Bevy 0.7

Version 0.4

• insert_some_or_else methods. If present, insert the inner value of an Option, otherwise insert the alternative value

New for Version 0.3

• insert_some methods. If present, insert the inner value of an Option.

Version 0.2

• Implementated traits for EntityMut.

• *_if_else methods.

  use conditional_commands::*;
  
  #[derive(Component)]
  struct Even;
  
  #[derive(Component)]
  struct Odd;
  
  fn exclusive_system(world: &mut World) {
      for n in 0..10 {
          world.spawn()
          .insert_if_else(n % 2 == 0, Even, Odd);
      }
  }
  

Usage

Add to your Cargo.toml [Dependencies] section

conditional_commands = "0.2"

Then access with the use declaration

use conditional_commands::*;

Motivating Contrived ECS Fizz-Buzz Example

use bevy::prelude::*;

#[derive(Component)]
struct Number(usize);

#[derive(Component)]
struct Fizz;

#[derive(Component)]
struct Buzz;

fn fizz_buzz<const N: usize>(
    mut commands: Commands
) {
    for n in 1 ..= N {
        let mut entity_commands = commands.spawn();
        if n % 3 {
            (0, 0) => { entity_commands.insert_bundle((Fizz, Buzz)); },
            (0, _) => { entity_commands.insert(Fizz); },
            (_, 0) => { entity_commands.insert(Buzz); },
            _ => { entity_commands.insert(Number(n)); }
        }
    }
}

With Conditional Commands we no longer need the intermediate EntityCommands binding.

use conditional_commands::*;

fn fizz_buzz<const N: usize>(
    mut commands: Commands
) {
    for n in 1 ..= N {
        commands
        .spawn()
        .insert_if(0 < n % 3 && 0 < n % 5, Number(n))
        .insert_if(n % 3 == 0, Fizz)
        .insert_if(n % 5 == 0, Buzz);
    }
}