添加设计模式及例子，包括：单例、抽象工厂、适配器、桥接、观察者模式

DesignPattern/ObserverPattern/ObserverMain.cpp

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+//
+// Created by xiemenghui on 2018/7/21.
+//
+
+#include "ObserverMain.h"
+
+void ObserverMain()
+{
+    // <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
+    ConcreteSubject * pSubject = new ConcreteSubject();
+
+    // <20><><EFBFBD><EFBFBD><EFBFBD>۲<EFBFBD><DBB2><EFBFBD>
+    IObserver * pObserver1 = new ConcreteObserver("Jack Ma");
+    IObserver * pObserver2 = new ConcreteObserver("Pony");
+
+    // ע<><D7A2><EFBFBD>۲<EFBFBD><DBB2><EFBFBD>
+    pSubject->Attach(pObserver1);
+    pSubject->Attach(pObserver2);
+
+    // <20><><EFBFBD>ļ۸񣬲<DBB8>֪ͨ<CDA8>۲<EFBFBD><DBB2><EFBFBD>
+    pSubject->SetPrice(12.5);
+    pSubject->Notify();
+
+    // ע<><D7A2>һ<EFBFBD><D2BB><EFBFBD>۲<EFBFBD><DBB2><EFBFBD>
+    pSubject->Detach(pObserver2);
+
+    // <20>ٴθ<D9B4><CEB8><EFBFBD>״̬<D7B4><CCAC><EFBFBD><EFBFBD>֪ͨ<CDA8>۲<EFBFBD><DBB2><EFBFBD>
+    pSubject->SetPrice(15.0);
+    pSubject->Notify();
+
+    SAFE_DELETE(pObserver1);
+    SAFE_DELETE(pObserver2);
+    SAFE_DELETE(pSubject);
+}