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/AbstractFactoryPattern/Factory.cpp

@@ -0,0 +1,25 @@
+//
+// Created by xiemenghui on 2018/7/20.
+//
+
+#include "Factory.h"
+#include "concrete_factory.h"
+
+Factory* Factory::CreateFactory(FACTORY_TYPE factory)
+{
+    Factory *pFactory = nullptr;
+    switch (factory) {
+        case FACTORY_TYPE::BENZ_FACTORY:  // 奔驰工厂
+            pFactory = new BenzFactory();
+            break;
+        case FACTORY_TYPE::BMW_FACTORY:  // 宝马工厂
+            pFactory = new BmwFactory();
+            break;
+        case FACTORY_TYPE::AUDI_FACTORY:  // 奥迪工厂
+            pFactory = new AudiFactory();
+            break;
+        default:
+            break;
+    }
+    return pFactory;
+}