What is the Rule of Three/Five/Zero?

Question

Accepted Answer

**Rule of Three** — if you define any of destructor, copy constructor, copy assignment, define all three.

**Rule of Five** — add move constructor and move assignment:
```cpp
class Buffer {
    char* data;
    size_t size;
public:
    ~Buffer();
    Buffer(const Buffer&);
    Buffer& operator=(const Buffer&);
    Buffer(Buffer&&) noexcept;
    Buffer& operator=(Buffer&&) noexcept;
};
```

**Rule of Zero** — prefer classes that don't manage resources directly:
```cpp
// Use RAII members instead
class Person {
    std::string name;
    std::vector<int> scores;
    // Compiler-generated special members are correct
};
```

**Best practice:** Follow Rule of Zero when possible.

C++: What is the Rule of Three/Five/Zero?