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  1. #include <memory>
  2. #include <iostream>
  3.  
  4. namespace poco { 
  5.   struct Parser 
  6.   { 
  7.     void reset() { std::cout << "Parser::reset !" << std::endl; } 
  8.     void print() { std::cout << "Parser::print !" << std::endl; }
  9.   }; 
  10. }
  11.  
  12. class MyParserBuilder
  13. {
  14. public:
  15.  
  16.   class MyParser
  17.   {
  18.   public:
  19.     MyParser(poco::Parser& parser, MyParserBuilder& builder) : 
  20.     _parser(parser), 
  21.     _builder(builder)
  22.     {
  23.  
  24.     }
  25.  
  26.     ~MyParser() 
  27.     { 
  28.       _builder.reset(); 
  29.     }
  30.  
  31.    // Either expose some functions from the parser or use 
  32.    // something like:
  33.     poco::Parser& operator*() { return _parser; }
  34.  
  35.   private:
  36.     poco::Parser& _parser;
  37.     MyParserBuilder& _builder;
  38.   };
  39.  
  40.   MyParserBuilder() : _used{false} {}
  41.  
  42.   std::unique_ptr<MyParser> build() 
  43.   { 
  44.       if (_used) // Or lock ?
  45.       {
  46.         return std::unique_ptr<MyParser>();
  47.       }
  48.       _used = true;
  49.       return std::unique_ptr<MyParser>(new MyParser(_parser, *this)); 
  50.     }
  51.  
  52.     void reset()
  53.     {
  54.       _parser.reset();
  55.       _used = false;
  56.     }
  57.  
  58.   private:
  59.     bool _used; 
  60.     poco::Parser _parser;
  61. };
  62.  
  63. int main(int, char*[])
  64. {
  65.   MyParserBuilder builder;
  66.  
  67.   for (unsigned long index = 0; index < 2; ++index)
  68.   {
  69.     auto parser1 = builder.build();
  70.     auto parser2 = builder.build();
  71.  
  72.     if (parser1)
  73.     {
  74.       std::cout << "Parser 1: " << std::endl;
  75.       (**parser1).print();
  76.     }
  77.  
  78.     if (parser2)
  79.     {
  80.       std::cout << "Parser 2: " << std::endl;
  81.       (**parser2).print();
  82.     }
  83.   }
  84. }
  85.  
Success #stdin #stdout 0s 3428KB
comments (?)
stdin
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Standard input is empty
stdout
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Parser 1: 
Parser::print !
Parser::reset !
Parser 1: 
Parser::print !
Parser::reset !
https://ideone.com/6wwg20
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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