DecoratorTest

Author: xiao cheng

CMakeLists.txt

@@ -19,4 +19,5 @@ if(Boost_FOUND)
     add_subdirectory(Proto)
     add_subdirectory(ObjectPool)
     add_subdirectory(RAII)
+    add_subdirectory(Decorator)
 endif()

Decorator/CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.8)
+
+project(Decorator)
+
+include_directories(${Boost_INCLUDE_DIRS})
+
+add_executable(Decorator decoratorTest.cpp)
+target_link_libraries(Decorator PUBLIC gtest_main ${Boost_LIBRARIES})
+
+install(TARGETS Decorator RUNTIME DESTINATION ../bin)

Decorator/decoratorTest.cpp

@@ -0,0 +1,128 @@
+#include <string>
+#include <memory>
+#include <iostream>
+
+using namespace std;
+
+struct IShape
+{
+    virtual auto draw() -> void = 0;
+    virtual auto description() -> std::string = 0;
+    virtual ~IShape() = default;
+};
+
+// Component class
+class Square : public IShape
+{
+  public:
+    auto draw() -> void
+    {
+        std::cout << " => Draw square" << std::endl;
+    }
+    auto description() -> std::string
+    {
+        return "square";
+    }
+};
+
+// Component class
+class Triangle : public IShape
+{
+  public:
+    auto draw() -> void
+    {
+        std::cout << " => Draw tringle" << std::endl;
+    }
+    auto description() -> std::string
+    {
+        return "triangle";
+    }
+};
+
+// Decorator 1 => Draw shape with color
+class ColorDecorator : public IShape
+{
+  public:
+    ColorDecorator(std::shared_ptr<IShape> shape)
+        : m_shape(shape) {}
+    auto draw() -> void
+    {
+        // Save color:   push()
+        std::cout << " => [ColorDecorator] Draw object with color blue" << std::endl;
+        m_shape->draw();
+        // Restore color: pop()
+    }
+    auto description() -> std::string
+    {
+        return m_shape->description() + " ; color = " + m_color;
+    }
+    // Return a reference to itself (ColorDecorator&)
+    auto setColor(const std::string &color) -> decltype(*this) &
+    {
+        m_color = color;
+        return *this;
+    }
+
+  private:
+    // The decorator owns the decorated object
+    std::shared_ptr<IShape> m_shape;
+    std::string m_color = "blue";
+};
+
+class PositionDecorator : public IShape
+{
+  public:
+    PositionDecorator(std::shared_ptr<IShape> shape)
+        : m_shape(shape) {}
+
+    auto draw() -> void
+    {
+        // Save transformation matrix:   pushMatrix()
+        std::cout << " =>  [PositionDecorator] Draw object at x = "
+                  << m_x << " ; y = " << m_y << std::endl;
+        m_shape->draw();
+        // Restore transformation matrix: popMatrix()
+    }
+    auto description() -> std::string
+    {
+        return m_shape->description() + " ; position x  = " + std::to_string(m_x) + " , y = " + std::to_string(m_y);
+    }
+    auto setPosition(double x, double y) -> PositionDecorator &
+    {
+        m_x = x, m_y = y;
+        return *this;
+    }
+
+  private:
+    // The decorator owns the decorated object
+    std::shared_ptr<IShape> m_shape;
+    int m_x = 0, m_y = 0;
+};
+
+int main()
+{
+    std::puts("\n ======>> Experiment 1 <<===========");
+    auto shape = std::make_shared<ColorDecorator>(std::make_shared<Square>());
+    shape->setColor("yellow");
+    shape->draw();
+
+    std::puts("\n ======>> Experiment 2 <<===========");
+    auto observerd = std::shared_ptr<IShape>{nullptr};
+
+    auto shapeWithColorAndPosition =
+        [&observerd] {
+            auto shape = std::make_shared<Triangle>();
+            observerd = shape;
+            auto shapeColored = std::make_shared<ColorDecorator>(shape);
+            shapeColored->setColor("white");
+            auto shapePos = std::make_shared<PositionDecorator>(shapeColored);
+            return shapePos;
+        }();
+
+    shapeWithColorAndPosition->setPosition(100, 20);
+    shapeWithColorAndPosition->draw();
+    std::cout << " DESCRIPTION = "
+              << shapeWithColorAndPosition->description() << std::endl;
+
+    std::cout << " [INFO] observed shape = " << observerd->description() << std::endl;
+}