具有动态对象的std :: array是否安全？

Question

Is it safe to have a std::array of dynamic object, for example std::array<std::string, 3> , and to resize the contents (the strings) ? (because it can be problematic to have a raw C array of strings)

Answer 1

Yes, because std::array is a just a friendly template that wraps an underlying C style aray array. You can think of it as something like this:

template <typename T, int size>
class Array {
...
   T vals[size];
}

Change T to string above and you'll quickly realize that anything that you can do to the contents of an array of strings you can do with a std::array of strings. This includes resizing, deleting, whatever you can imagine.

To think even deeper about it, think about it this way. The std::array holds a string. The string has no idea where its being held. The array might tell the string to make a copy of itself (through a copy constructor or assignment), when say the array itself is assigned. However, this is its entirely through the string's public interface. The fact that the string is being held by any data structure doesn't limit that string's functionality, it just makes the holder (in this case std::array ) yet another client of the string 's public interface.

As containers like std::array need to work with a large variety of types, they tend to make relatively few typically well documented assumptions on the type T passed in. Stuff like requiring that T can be copy constructed, default constructed, and assigned. Then its typically up to the implementer* of T to ensure these few assumptions are valid.

_{*There is a very advanced topic called template specialization where one could write a specialized version of array just for say "string". Aside from vector<bool> these are pretty rare with the standard containers.}

Answer 2

假设您的意思是调整字符串的大小，那么可以。