Should a std::vector of objects use pointers, references, or nothing?

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Suppose we have some class, say class Apple, and wanted to store a std::vector containing Apple.

Should the vector contain pointers, references, or plain objects?

std::vector<Apple*> vector; // Definitely won't copy the Apple on lookup,      // but I would prefer not to use pointers if I don't have to std::vector<Apple&> vector; // Seems circuitous? std::vector<Apple> vector; // I don't know if this copies the Apple on each lookup 

My goal is to make it so when I call

Apple& a = vector[4]; 

the Apple won't get copied.

I've been using C++ for over a year and I've always worked around this and never understood it. Is there a simple explanation of why one of these three approaches is the best practice?

 


Use the type T. Remember that operator[] returns a (const) reference, so your Apple& works fine there:

      T& vector<T>::operator[](size_t); const T& vector<T>::operator[](size_t) const; 

That's why you can use vec[3].make_older() to begin with if return_type Apple::make_older(void) exists.

However, keep in mind that there are many methods that invalidate references, so

Apple& reference = vec[3]; vec.push_back(other_apple);  reference.get_eaten(); 

might result in undefined behaviour if push_back reallocated the referenced apple.

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