(C++) Strategy Design Pattern Example: StrToDouble

 

Strategy Design Pattern Example: StrToDouble is an example of a Strategy Design Pattern.

 

You can convert this to a compile-time Strategy Design Pattern, for example to compile-time Strategy Design Pattern example: StrToDouble.

 

• Download the Qt Creator project 'CppStrategyDesignPatternExampleStrToDouble' (zip)

 

 

 

 

 

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 12.10 (quantal)

IDE(s):

• Qt Creator 2.5.2

Project type:

• Console application

C++ standard:

• C++11

Compiler(s):

• G++ 4.7.2

Libraries used:

• STL: GNU ISO C++ Library, version 4.7.2

 

 

 

 

 

Qt project file: CppStrategy Design Pattern Example: StrToDouble.pro

 

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TEMPLATE = app CONFIG += console CONFIG -= qt QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++ SOURCES += main.cpp

 

 

 

 

 

main.cpp

 

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#include <boost/lexical_cast.hpp> #include <boost/shared_ptr.hpp> #include <string> ///A Strategy Design Pattern struct StrToDoubleStrategy {   virtual double StrToDouble(const std::string& s) const = 0;   virtual ~StrToDoubleStrategy() {} }; struct StrToDoubleStrategyStl : public StrToDoubleStrategy {   double StrToDouble(const std::string& s) const   {     return std::atof(s.c_str());   } }; struct StrToDoubleStrategyBoost : public StrToDoubleStrategy {   double StrToDouble(const std::string& s) const   {     return boost::lexical_cast<double>(s);   } }; struct StrToDoubleStrategyCpp11 : public StrToDoubleStrategy {   double StrToDouble(const std::string& s) const   {     return std::stof(s);   } }; struct Converter {   Converter(const StrToDoubleStrategy * strategy)     : m_strategy(strategy)   {     assert(m_strategy);   }   double StrToDouble(const std::string& s) const   {     return m_strategy->StrToDouble(s);   }   private:   boost::shared_ptr<const StrToDoubleStrategy> m_strategy; }; #include <cassert> int main() {   const Converter a(new StrToDoubleStrategyStl);   const Converter b(new StrToDoubleStrategyBoost);   const Converter c(new StrToDoubleStrategyCpp11);   assert( std::abs(12.34 - a.StrToDouble("12.34")) < 0.000001);   assert( std::abs(12.34 - b.StrToDouble("12.34")) < 0.000001);   assert( std::abs(12.34 - c.StrToDouble("12.34")) < 0.000001); }