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  1. #include <iostream>
  2. #include <memory>
  3.  
  4.  
  5. // a dummy QDebug class, don't have QT installed here
  6. class QDebug {};
  7. QDebug& qDebug() {
  8.     static QDebug obj;
  9.     return obj;
  10. }
  11. template <typename T>
  12. QDebug& operator <<(QDebug &os, const T &value) {
  13.     std::cout << "QDebug: " << value << std::endl;
  14.     return os;
  15. }
  16. // end dummy class
  17.  
  18.  
  19. class ILoggableValue {
  20. public:
  21.     virtual ~ILoggableValue() = default;
  22.     virtual void log(QDebug &os) const = 0;
  23.     virtual void log(std::ostream &os) const = 0;
  24. };
  25.  
  26. template <typename T>
  27. class LoggableValue : public ILoggableValue {
  28. public:
  29.     LoggableValue(const T &value) : value{value} {}
  30.     void log(QDebug &os) const override {
  31.         // implementation of log for QDebug goes here
  32.         os << value;
  33.     }
  34.     void log (std::ostream &os) const override {
  35.         // implementation of log for std::ostream goes here
  36.         os << value << std::endl;
  37.     }
  38. private:
  39.     const T &value;
  40. };
  41.  
  42.  
  43. class IHandler {
  44. public:
  45.     virtual ~IHandler() = default;
  46.     virtual void log(const ILoggableValue &tolog) const = 0;
  47. };
  48.  
  49. class CLHandler : public IHandler {
  50. public:
  51.     explicit CLHandler(std::ostream &out) : out{out} {} 
  52.     void log(const ILoggableValue &tolog) const override {
  53.         tolog.log(out);
  54.     }
  55. private:
  56.     std::ostream &out;
  57. };
  58.  
  59. class UIHandler : public IHandler {
  60. public:
  61.     void log(const ILoggableValue &tolog) const override {
  62.         tolog.log(qDebug());
  63.     }
  64. };
  65.  
  66.  
  67. class Logger {
  68. public:
  69.     Logger(std::unique_ptr<IHandler> h) : handler(std::move(h)) {}
  70.     template <class T>
  71.     void log(const T& tolog) { handler->log(LoggableValue<T>(tolog)); }
  72.  
  73.     void setHandler(std::unique_ptr<IHandler> &h) { handler = std::move(h); }
  74.     const IHandler &getHandler() const { return *handler; }
  75.  
  76. private:
  77.     std::unique_ptr<IHandler> handler;
  78. };
  79.  
  80.  
  81. // example
  82. void example(Logger &logger) {
  83.     logger.log(5);
  84.     logger.log("ABC");
  85.     logger.log(4.2);
  86. }
  87.  
  88. int main() {
  89.     Logger qLogger{std::make_unique<UIHandler>()};
  90.     example(qLogger);
  91.     Logger stdoutLogger{std::make_unique<CLHandler>(std::cout)};
  92.     example(stdoutLogger);
  93. }
  94.  
Success #stdin #stdout 0s 4140KB
comments (?)
stdin
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Standard input is empty
stdout
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QDebug: 5
QDebug: ABC
QDebug: 4.2
5
ABC
4.2
https://ideone.com/0Urp1M
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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