On Fri, Dec 18, 2009 at 9:36 AM, Conoscenza Silente
Hi All I am trying to use boost lambda for looping over a std::map to get each element and pass those to a class function using lambda functions. I don't know why but the binding inside my std::for_each is not compiling and I have 2 errors pointing to the line where boost::assign is used.
'invalid initialization of reference of type int&' 'invalid initialization of reference of type std::basic_string<>&'
Do you know how to fix this and why it is happening Thank you very much Regards CS
//Boost //#include
#include #include
#include #include #include class CInnerClassHandler{ public: void DoSomething( int aIntValue, const std::string& aStringValue ){
std::cout << "INT:" << aIntValue << "STRING:" << aStringValue << std::endl; // here we just trace } };
void map_lambda_test(){
typedef std::pair< int, std::string > this_pair;
std::map< int, std::string > dictionary = boost::assign::map_list_of(3,"A")(4,"B")(5,"C"); // Errors points to // this line of code
CInnerClassHandler obj;
std::for_each( dictionary.begin(), dictionary.end(), boost::lambda::bind( &CInnerClassHandler::DoSomething, &obj, boost::lambda::bind(&this_pair::first, boost::lambda::_1), boost::lambda::bind(&this_pair::second,boost::lambda::_1)) ); }
The errors are because this_pair doesn't accurately define the pair passed to the lambda function - maps actually use a pair with a const key. Try using this typedef for this_pair instead: typedef std::map< int, std::string >::value_type this_pair; HTH Stuart Dootson