Indexing operator of an object owned by unique_ptr

Question

I am working on a C++ project. I need to put different classes into std::vector. I found that this indeed is possible by creating classes with a common type and then putting pointers in the vector. In this case, I could cast the pointers to the type I need. That much is clear to me.

It is also mentioned that in principle it is possible to use not just pointers but smart pointers, i.e, std::vector<std::unique_ptr<TMyClass>>. This is where my problem begins. TMyClass has the indexing operator (operator[]).

Let's say I have std::vector<std::unique_ptr<TMyClass>> A. I try to access an element of the TMyClass object like A[0][0] or A[0].get()[0] or (A[0])[0], but when I compile I get an error:

[bcc64 Error] type 'value_type' (aka 'std::unique_ptr<.....>') does not provide a subscript operator

How can I tell the compiler that the second index is related to the TMyClass object and not to unique_ptr? I would highly appreciate if somebody would explain to me how to access elements in this case.

Answer 1

You need to extract pointer first

A[0]  //type: std::unique_ptr<TMyClass>&

Then extract object from that pointer (pointee)

*A[0] //type: TMyClass&

And then you can use your overloaded operators on this object

(*A[0])[0]