Question

In my program, I have a map with string keys and list (of a user-defined class) values, defined like so:

std::map<const char*, std::list<Show>> _shows;

I have a function that adds to a specific list, like so:

void Add(Show s, const char* index) {
list<Show> lshow = _shows[index];
lshow.push_back(s); }

However, every time the function is called with the same index, rather than returning the same list, I get an empty list.

What am I doing wrong?

ETA: I see the number of values in the dictionary increases after each time I call the function. Could this be [] operator related?

Answer 1

The key in your map is the pointer value, not its contents. Therefore weird behavior. Change the map so that its key be std::string. Also, you modify the copy of your stored list. To avoid this, use a reference

list<Show>& ls = map[index]