Under what circumstances must I provide, assignment operator, copy constructor and destructor for my C++ class? [duplicate]

Question

Say I've got a class where the sole data member is something like std::string or std::vector. Do I need to provide a Copy Constructor, Destructor and Assignment Operator?

Answer 1

In case your class contains only vector/string objects as its data members, you don't need to implement these. The C++ STL classes (like vector, string) have their own copy ctor, overloaded assignment operator and destructor.

But in case if your class allocates memory dynamically in the constructor then a naive shallow copy will lead to trouble. In that case you'll have to implement copy ctor, overloaded assignment operator and destructor.

Answer 2

The usual rule of thumb says: if you need one of them, then you need them all.

Not all classes need them, though. If you class holds no resources (memory, most notably), you'll be fine without them. For example, a class with a single string or vector constituent doesn't really need them - unless you need some special copying behavior (the default will just copy over the members).