Question

I’d like to use std::array from C++11 as a field of my own class. It takes two template parameters (first defines type of data, second defines size of an array).

But I know the second parameter only in constructor. I’m not familiar with C++11 standard, but I suppose that it’s impossible to set a template parameter during execution.

Are there any alternatives for std::array? std::vector is probably a little too much, cause I will never change the size of it.

Answer 1

std::vector is the simplest thing to use; although as you say, it does waste a few bytes if you’ll never need to resize it.

std::unique_ptr<T[]>, initialised using the result of new T[size], would be the most efficient thing; it should be the same size as a pointer, and will delete the allocated memory for you when it’s destroyed. It’s not copyable, though; you’ll need to provide a copy constructor for your class if you want it to be copyable. It’s also less convenient than std::array and std::vector, since it doesn’t have the interface of a standard container. You could perhaps write a STL-style wrapper for it if you need that; but I’d just use std::vector in that case.