From 0b9fd0921d480caf41719c14be13cd3a0525c7cd Mon Sep 17 00:00:00 2001
From: Nolan Darilek <nolan@thewordnerd.info>
Date: Fri, 11 Feb 2022 11:28:42 -0600
Subject: [PATCH] Add `RunIfExists` command for only executing if a given
 entity exists.

---
 src/commands.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 src/commands.rs

diff --git a/src/commands.rs b/src/commands.rs
new file mode 100644
index 0000000..129f4c6
--- /dev/null
+++ b/src/commands.rs
@@ -0,0 +1,22 @@
+use bevy::{
+    ecs::{system::Command, world::EntityMut},
+    prelude::*,
+};
+
+struct RunIfExistsCommand<F>(Entity, F);
+
+impl<F: FnOnce(EntityMut) + Send + Sync + 'static> Command for RunIfExistsCommand<F> {
+    fn write(self, world: &mut World) {
+        world.get_entity_mut(self.0).map(self.1);
+    }
+}
+
+pub trait RunIfExistsExt {
+    fn run_if_exists(&mut self, entity: Entity, f: impl FnOnce(EntityMut) + Send + Sync + 'static);
+}
+
+impl RunIfExistsExt for Commands<'_, '_> {
+    fn run_if_exists(&mut self, entity: Entity, f: impl FnOnce(EntityMut) + Send + Sync + 'static) {
+        self.add(RunIfExistsCommand(entity, f));
+    }
+}