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| #include <cstdlib>
#include <ctime>
#include <iostream>
#include <typeinfo>
#include <unordered_map>
#include <sstream>
namespace std {
// Patch because MinGW doesn't know std::to_string()
// See http://stackoverflow.com/questions/12975341/to-string-is-not-a-member-of-std-says-g
template<typename T> std::string to_string(const T& n) {
std::ostringstream stm;
stm << n;
return stm.str();
}
}
//--- Service manager-----------------------------------------------
class Service {
// The purpose of this class is meant to have a common type for all service classes
// so that the ServiceManager can handle them
};
class ServiceHasher {
public:
unsigned long operator()(const std::type_info* info) const {
return (unsigned long) info;
}
};
class ServiceManager {
public:
template<class ServiceInterface>
void registerService(ServiceInterface* service) {
service_map[&typeid(ServiceInterface)] = service;
}
template<class ServiceInterface>
ServiceInterface& getService() {
return (ServiceInterface&) *service_map[&typeid(ServiceInterface)];
}
private:
std::unordered_map<const std::type_info*, Service*, ServiceHasher> service_map;
};
//--- Service interfaces--------------------------------------------
class PrinterService: public Service {
public:
virtual ~PrinterService() {
}
virtual void print(std::string) = 0;
};
class TemperatureService: public Service {
public:
virtual ~TemperatureService() {
}
virtual double getTemperature() = 0;
virtual std::string getUnit() = 0;
};
//--- Service implementations---------------------------------------
class StandardPrinter: public PrinterService {
public:
void print(std::string text) {
std::cout << text << std::endl;
}
};
class OutsideTemperature: public TemperatureService {
public:
double getTemperature(void) {
std::srand(std::time(0));
return (double) std::rand() + (double) std::rand() / 10;
}
std::string getUnit(void) {
return "°C";
}
};
//--- Application---------------------------------------------------
ServiceManager manager;
void init(void) {
// Create services
OutsideTemperature* temperature = new OutsideTemperature;
StandardPrinter* printer = new StandardPrinter;
// Register them
manager.registerService<TemperatureService>(temperature);
manager.registerService<PrinterService>(printer);
}
void run(void) {
TemperatureService& temperatureService = manager.getService<
TemperatureService>();
PrinterService& printerService = manager.getService<PrinterService>();
double temperature = temperatureService.getTemperature();
std::string unit = temperatureService.getUnit();
std::string message = std::to_string(temperature) + unit;
printerService.print(message);
}
int main(int argc, char **argv) {
init();
run();
} |
