Iterator invalidation in boost::unordered_map

Question

I am using boost::unordered_map as follows

typedef boost::shared_ptr PtrWriter;
typedef std::list PtrLis         


        

Answer 1

The erase() operation will invalidate the iterator. However, it also returns a valid iterator to the next element. So you can use something like the following:

for(auto it = instrMap.begin(); it != instrMap.end();)
{
     auto key = it->first();
     auto list& = it->second();    
     //Make some change to an element in list 

      if(list.empty())
      {
            it = instMap.erase(it); 
      }
      else {
            ++it;
      }
}