From ef4093c5ba38caa38a9f9ebabd2ef02c5416a223 Mon Sep 17 00:00:00 2001
From: "Glenn Y. Rolland" <glenux@glenux.net>
Date: Sun, 3 Jan 2021 21:30:58 +0100
Subject: [PATCH] Add observable design pattern implementation

---
 src/lib/observable.cr | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 src/lib/observable.cr

diff --git a/src/lib/observable.cr b/src/lib/observable.cr
new file mode 100644
index 0000000..6c7093e
--- /dev/null
+++ b/src/lib/observable.cr
@@ -0,0 +1,21 @@
+
+# Code from: https://github.com/crystal-community/crystal-patterns
+# Licence:   MIT
+
+module Observable(T)
+  getter observers
+
+  def add_observer(observer)
+    @observers ||= [] of T
+    @observers.not_nil! << observer
+  end
+
+  def delete_observer(observer)
+    @observers.try &.delete(observer)
+  end
+
+  def notify_observers
+    @observers.try &.each &.update self
+  end
+end
+