From 13da707aeef0084a9194f2fc1202648581fb7281 Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Sun, 29 Mar 2020 23:51:13 -0700
Subject: [PATCH] add event example

---
 examples/event.rs      | 43 ++++++++++++++++++++++++++++++++++++++++++
 src/app/app_builder.rs |  7 ++++++-
 src/prelude.rs         | 18 ++++++++++++------
 3 files changed, 61 insertions(+), 7 deletions(-)
 create mode 100644 examples/event.rs

diff --git a/examples/event.rs b/examples/event.rs
new file mode 100644
index 0000000000..8ba456d65a
--- /dev/null
+++ b/examples/event.rs
@@ -0,0 +1,43 @@
+use bevy::prelude::*;
+
+struct MyEvent {
+    pub message: String,
+}
+
+fn main() {
+    App::build()
+        .add_defaults()
+        .add_event::<MyEvent>()
+        .add_system(event_trigger_system())
+        .build_system(event_listener_system)
+        .run();
+}
+
+fn event_trigger_system() -> Box<dyn Schedulable> {
+    let mut elapsed = 0.0;
+    SystemBuilder::new("EventTrigger")
+        .read_resource::<Time>()
+        .write_resource::<Event<MyEvent>>()
+        .build(move |_, _, (time, my_event), _| {
+            elapsed += time.delta_seconds;
+            if elapsed > 1.0 {
+                my_event.raise(MyEvent {
+                    message: "Hello World".to_string(),
+                });
+
+                elapsed = 0.0;
+            }
+        })
+}
+
+fn event_listener_system(resources: &mut Resources) -> Box<dyn Schedulable> {
+    let my_event = resources.get::<Event<MyEvent>>().unwrap();
+    let mut my_event_handle = my_event.get_handle();
+    SystemBuilder::new("EventListener")
+        .read_resource::<Event<MyEvent>>()
+        .build(move |_, _, my_events, _| {
+            for my_event in my_events.iter(&mut my_event_handle) {
+                println!("{}", my_event.message);
+            }
+        })
+}
diff --git a/src/app/app_builder.rs b/src/app/app_builder.rs
index b8fa14bbe8..5f75999356 100644
--- a/src/app/app_builder.rs
+++ b/src/app/app_builder.rs
@@ -119,12 +119,17 @@ impl AppBuilder {
     pub fn add_system(self, system: Box<dyn Schedulable>) -> Self {
         self.add_system_to_stage(system_stage::UPDATE, system)
     }
-
+    
     pub fn add_setup_system(mut self, system: Box<dyn Schedulable>) -> Self {
         self.setup_systems.push(system);
         self
     }
 
+    pub fn build_system<F>(mut self, build: F) -> Self where F: Fn(&mut Resources) -> Box<dyn Schedulable>{
+        let system = build(&mut self.resources);
+        self.add_system(system)
+    }
+
     pub fn add_system_to_stage(mut self, stage_name: &str, system: Box<dyn Schedulable>) -> Self {
         if let None = self.system_stages.get(stage_name) {
             self.system_stages
diff --git a/src/prelude.rs b/src/prelude.rs
index 8629c815dc..cdcf55d523 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -1,11 +1,11 @@
 pub use crate::{
     app::{App, AppBuilder, plugin::AppPlugin},
     asset::{Asset, AssetStorage, Handle},
-    core::{Time, Window},
+    core::{Time, Window, Event, EventHandle},
     ecs,
     ecs::{
         default_archetypes::*, CommandBufferBuilderSource, EntityArchetype, WorldBuilder,
-        WorldBuilderSource,
+        WorldBuilderSource
     },
     render::{
         mesh::{Mesh, MeshType},
@@ -23,11 +23,17 @@ pub use bevy_derive::*;
 pub use bevy_transform::prelude::*;
 pub use glam as math;
 pub use legion::{
-    prelude::*,
-    prelude::Event as LegionEvent,
+    command::CommandBuffer,
+    entity::Entity,
+    event::Event as LegionEvent,
+    filter::filter_fns::*,
+    query::{IntoQuery, Query, Read, Tagged, TryRead, TryWrite, Write},
+    world::{Universe, World},
     systems::{
-        schedule::{Builder, Schedulable},
-        SubWorld, SystemBuilder,
+        bit_set::BitSet,
+        resource::{ResourceSet, Resources},
+        schedule::{Executor, Runnable, Schedulable, Schedule},
+        System, SystemBuilder, SubWorld
     },
 };
 pub use math::{Mat3, Mat4, Quat, Vec2, Vec3, Vec4};