Upload strategy design pattern example

Author: XuhuaHuang

DesignPattern/strategy.cpp

@@ -0,0 +1,105 @@
+/**
+ * @file strategy.cpp
+ * @author Xuhua Huang
+ * @brief 
+ * https://compiler-explorer.com/z/eKfjKscPv
+ *
+ * @version 0.1
+ * @date 2026-04-12
+ *
+ * @copyright Copyright (c) 2026
+ *
+ */
+
+#include <iomanip>
+#include <iostream>
+#include <memory>
+#include <sstream>
+#include <string>
+
+class date_t;
+
+class date_formatter_t {
+public:
+  virtual ~date_formatter_t() = default;
+
+  virtual std::string to_string(const date_t& date) const = 0;
+};
+
+class date_t {
+public:
+  date_t(int y, int m, int d, int h, int min, int s, std::unique_ptr<date_formatter_t> formatter)
+    : m_year(y)
+    , m_month(m)
+    , m_day(d)
+    , m_hour(h)
+    , m_minute(min)
+    , m_second(s)
+    , m_formatter(std::move(formatter)) {}
+
+  void set_formatter(std::unique_ptr<date_formatter_t> formatter) { m_formatter = std::move(formatter); }
+
+  std::string to_string() const { return m_formatter->to_string(*this); }
+
+  inline int year() const { return m_year; }
+  inline int month() const { return m_month; }
+  inline int day() const { return m_day; }
+  inline int hour() const { return m_hour; }
+  inline int minute() const { return m_minute; }
+  inline int second() const { return m_second; }
+
+private:
+  int m_year;
+  int m_month;
+  int m_day;
+  int m_hour;
+  int m_minute;
+  int m_second;
+
+  std::unique_ptr<date_formatter_t> m_formatter;
+};
+
+class date_only_formatter_t : public date_formatter_t {
+public:
+  std::string to_string(const date_t& date) const override {
+    std::ostringstream os;
+    os << std::setw(2) << std::setfill('0') << date.month() << "-" << std::setw(2) << std::setfill('0') << date.day()
+       << "-" << date.year();
+    return os.str();
+  }
+};
+
+class date_time_formatter_t : public date_formatter_t {
+public:
+  std::string to_string(const date_t& date) const override {
+    std::ostringstream os;
+    os << std::setw(2) << std::setfill('0') << date.month() << "-" << std::setw(2) << std::setfill('0') << date.day()
+       << "-" << date.year() << " " << std::setw(2) << std::setfill('0') << date.hour() << ":" << std::setw(2)
+       << std::setfill('0') << date.minute() << ":" << std::setw(2) << std::setfill('0') << date.second();
+    return os.str();
+  }
+};
+
+class time_only_formatter_t : public date_formatter_t {
+public:
+  std::string to_string(const date_t& date) const override {
+    std::ostringstream os;
+    os << std::setw(2) << std::setfill('0') << date.hour() << ":" << std::setw(2) << std::setfill('0') << date.minute()
+       << ":" << std::setw(2) << std::setfill('0') << date.second();
+    return os.str();
+  }
+};
+
+int main() {
+  date_t d(2011, 11, 5, 9, 52, 0, std::make_unique<date_only_formatter_t>());
+
+  std::cout << "date: " << d.to_string() << "\n";
+
+  d.set_formatter(std::make_unique<time_only_formatter_t>());
+  std::cout << "time: " << d.to_string() << "\n";
+
+  d.set_formatter(std::make_unique<date_time_formatter_t>());
+  std::cout << "datetime: " << d.to_string() << "\n";
+
+  return 0;
+}