Support serial async events via DispatchQueue.main

Excitation/Excitation.swift

@@ -45,7 +45,7 @@ public class Emitter<T> {
     }
 
     public func observe(_ f: @escaping ()->Void) -> Observer<T> {
-        return self.observe({ (_: T) in f() })
+        return self.observe { (_: T) in f() }
     }
     public func observe(_ f: @escaping (T)->Void) -> Observer<T> {
         let ob = Observer<T>(f)
@@ -55,6 +55,15 @@ public class Emitter<T> {
         obRef[ObjectIdentifier(ob)] = ob
         return ob
     }
+
+    public func observeAsync(_ f: @escaping ()->Void) -> Observer<T> {
+        return self.observeAsync { (_: T) in f() }
+    }
+    public func observeAsync(_ f: @escaping (T)->Void) -> Observer<T> {
+        return self.observe { data in
+            DispatchQueue.main.async { f(data) }
+        }
+    }
 
     public func remove(_ ob: Observer<T>) {
         nc.removeObserver(ob, name: nn, object: nil)

ExcitationTests/ExcitationTests.swift

@@ -33,4 +33,23 @@ class ExcitationTests: XCTestCase {
         e.remove(ob)
         e.emit()
     }
+
+    func testAsyncNoData() {
+        let e = Emitter<None>()
+        let ex = XCTestExpectation(description: "async event")
+        let _ = e.observeAsync { ex.fulfill() }
+        e.emit()
+        wait(for: [ex], timeout: 1)
+    }
+
+    func testAsyncWithData() {
+        let e = Emitter<Int>()
+        let ex = XCTestExpectation(description: "async event")
+        let _ = e.observeAsync { n in
+            XCTAssert( n == 1 )
+            ex.fulfill()
+        }
+        e.emit(1)
+        wait(for: [ex], timeout: 1)
+    }
 }

README.md

@@ -4,9 +4,9 @@
 [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
-A thin wrapper around NotificationCenter for supporting event-driven code.
+A thin wrapper around `NotificationCenter` and `DispatchQueue` for supporting event-driven code.
 
-Event handlers are dispatched synchronously as is NotificationCenter.
+Excitation supports both sync and async events via `DispatchQueue.main`.
 
 ## Install
 
@@ -37,12 +37,13 @@ e.observe {
 // Emit event
 e.emit()
 
-// Example: Event with Data
+// Example: Event with Data & Async
 // =====================================================
 
 let e = Emitter<Int>()
 e.observe { n in print(n) } // prints 1
-e.observe { print("hi") }   // prints hi
+e.observe { print("hi") }
+e.observeAsync { print("async handler") }
 e.emit(1)
 
 // Example: Remove Handlers