c++booststdstringflyweight-pattern

string to flyweights of string conversion: Better performance option

so i have a flyweight of strings type:

typedef boost::flyweight< std::string, boost::flyweights::intermodule_holder > SymbolName_t;

and i want to push a instance of this into a vector of them, but the naive approach won't work:

void PushSome( std::vector < SymbolName_t >& list)
{
  std::string& str = getSomeStr();
  list.push_back( str ); // <--- won't compile
}

so i added a temporary constructor:

void PushSome( std::vector < SymbolName_t >& list)
{
  std::string& str = getSomeStr();
  list.push_back( SymbolName_t(str) ); // <--- compiles ok
}

my question is: is this approach optimal, given the constraints of the language? what benefits would provide implementing this in some other way, say, by providing a static conversion operator? I don't consider a implicit conversion via a non-explicit constructor a valid option because that would require modifying the boost::flyweight template

Solution

  • If you have a C++11 compiler, you can use emplace_back instead of push_back, which eliminates the need for the copy.