Rule of zero

The “Rule of Zero” is a principle in C++ that suggests avoiding explicit resource management in your classes whenever possible. The rule states that if a class doesn’t need to manage any resources (such as dynamically allocated memory) or doesn’t need to define custom destructors, copy constructors, or copy assignment operators, then it’s best to rely on the compiler-generated default implementations.

By following the Rule of Zero, you allow the compiler-generated functions to handle resource management automatically, reducing the chances of errors and memory leaks. Instead, you can leverage smart pointers and other RAII (Resource Acquisition Is Initialization) techniques to manage resources.

Here’s an example illustrating the Rule of Zero in C++:

#include <iostream>
#include <memory>

// A class that follows the Rule of Zero
class MyClass {
private:
    std::unique_ptr<int> data;

public:
    // No custom destructor, copy constructor, or copy assignment operator

    void setData(int value) {
        data = std::make_unique<int>(value);
    }

    void printData() {
        if (data) {
            std::cout << "Data: " << *data << std::endl;
        } else {
            std::cout << "No data set." << std::endl;
        }
    }
};

int main() {
    MyClass obj1;
    obj1.setData(42);
    obj1.printData();

    MyClass obj2 = obj1;  // Copy construction
    obj2.printData();

    MyClass obj3;
    obj3 = obj2;  // Copy assignment
    obj3.printData();

    return 0;
}

In this example, the MyClass does not define a custom destructor, copy constructor, or copy assignment operator. The std::unique_ptr<int> member variable data automatically handles memory management, ensuring that the int value is deleted when the MyClass object goes out of scope.

By relying on the compiler-generated default implementations, we don’t have to worry about explicitly managing resources or writing our own destructors, which simplifies the code and reduces the chances of making mistakes.