Inserting an element with pointer to std::map using Index operator

Question

Say I have an std::map type which for example is defined as follows.

std::map<int, int>* someMap;

If I weren't using a pointer, I could simply add an element using the index operator. However in this case, since I have a pointer, would the following be the correct way to insert using the index operator.

(*someMap)[someIndex] = someValue;

Answer 1

Yes. The operator [] is overloaded for the Map class. It has to be used directly with the object.

Answer 2

Make sure you point someMap at something. Otherwise, its just contains a meaningless address derived from garbage on the stack. Here's an example allocating from the heap:

  std::map<int, int>* someMap = new std::map<int, int>();

and once thats done, yes, you are correct in how to use it:

  (*someMap)[someIndex] = someValue;

and be sure to cleanup after yourself

  delete someMap;

Answer 3

是的，您的代码很好：

(*someMap)[someIndex] = someValue;