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  1. #include<map>
  2. #include<string>
  3. #include<iostream>
  4. using namespace std;
  5.  
  6. struct IFoo{};
  7.  
  8. struct Factory
  9. {
  10.   struct Base{ virtual IFoo * build()const=0;  };
  11.  
  12.   typedef std::string Str;
  13.   typedef std::map<const Str, Base*> Map;
  14.   typedef Map::const_iterator It;
  15.   typedef Map::value_type ValType;
  16.  
  17.   template<class T> struct Builder : Base
  18.   { 
  19.     IFoo* build()const { return new T; };  
  20.   };
  21.  
  22.   template<class T> static void reg_class(const Str& key)
  23.   {
  24.       reg().insert( ValType(key, new Builder<T>())  );  
  25.   }
  26.  
  27.   static IFoo* build(const Str& key) 
  28.   {
  29.       It it = reg().find(key);
  30.       return (it==reg().end())? 0l : it->second->build() ;
  31.   }
  32. private:
  33.   static std::map<const Str, Base*>& reg(){ static Map data; return data; }
  34.  
  35. };
  36.  
  37. struct Bar0 : IFoo
  38. {
  39.     Bar0(){ cout<<"i am Bar0\n"; }
  40. };
  41. struct Bar1 : IFoo
  42. {
  43.     Bar1(){ cout<<"i am Bar1\n"; }
  44. };
  45.  
  46. int main()
  47. {
  48.     Factory::reg_class<Bar0>("Bar0");
  49.     Factory::reg_class<Bar1>("Bar1");
  50.  
  51.     //---------
  52.  
  53.     IFoo* ptr = Factory::build("Bar0");
  54. }
Success #stdin #stdout 0s 3476KB
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Standard input is empty
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i am Bar0
https://ideone.com/uRIveT
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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