C++ STL::map 包含 Z2523E0C272CB676C4F59F978289966

Question

I get the following error when trying to assign a element from a deque to a user defined class.

    map<unsigned int, std::deque<Order*>>::iterator itBuyPrices =buyPrices.begin();
    Order *buyOrder;
    buyOrder = itBuyPrices->second.pop_back();

ERROR at the assignment line (3rd line): Error C2440 '=': cannot convert from 'void' to 'Order *'

Answer 1

deque::pop_back() returns void , ie nothing. You need to use deque::back() to access the last item in the queue before then calling pop_back() to remove it, eg:

map<unsigned int, std::deque<Order*>>::iterator itBuyPrices = buyPrices.begin();
Order *buyOrder = itBuyPrices->second.back();
itBuyPrices->second.pop_back();