Improved

Author: sajith

CMakeLists.txt

@@ -20,4 +20,5 @@ set(CMAKE_CXX_STANDARD 20)
 #add_executable(lsp LSP/lsp_better_example.cpp)
 #add_executable(lspcovarient LSP/lsp_covariance_example.cpp)
 #add_executable(lspqueryset LSP/lsp_query_set.cpp)
-add_executable(isp_door ISP/isp_door_example.cpp)
+#add_executable(isp_door ISP/isp_door_example.cpp)
+add_executable(isp_door_better ISP/isp_door_example_better.cpp)

ISP/isp_door_example_better.cpp

@@ -0,0 +1,83 @@
+
+//
+// Created by sajith on 4/18/21.
+//
+
+#include <iostream>
+#include <optional>
+#include <stdexcept>
+
+class TimerClient
+{
+public:
+    virtual ~TimerClient() = default;
+    virtual void timeout() = 0;
+};
+
+class Door
+{
+public:
+    virtual ~Door() = default;
+    virtual void open() = 0;
+    virtual void close() = 0;
+};
+
+class Timer
+{
+    TimerClient &client;
+
+public:
+    Timer(TimerClient &client) : client{client}
+    {
+        client.timeout();
+    }
+};
+
+
+class TimedDoor : public Door, public TimerClient
+{
+    std::optional<Timer> timer;
+public:
+    void open()
+    {
+        std::cout << "Open\n";
+        timer.emplace(Timer(*this));
+    }
+
+    void close()
+    {
+        std::cout << "Close\n";
+    }
+
+    void timeout()
+    {
+        std::cout << "Timeout\n";
+        close();
+        timer = std::nullopt;
+    }
+};
+
+
+class NormalDoor : public Door
+{
+public:
+    void open()
+    {
+        std::cout << "Open\n";
+    }
+
+    void close()
+    {
+        std::cout << "Close\n";
+    }
+};
+
+int main()
+{
+    TimedDoor door;
+    door.open();
+    door.open();
+
+    return 0;
+}
+