How would you explain C++'s rule of 0, rule of 3, and rule of 5 in your own words?

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Ashish Kumar

Electrical Engineer from IIT Kanpur ,By profession Software Engineer and Teacher by passion

These rules are instrumental when you design your class. When you create/write a new class, you always think of 5 place holder methods in it. Earlier it was three, but after C++ 11 it became 5. They are: Constructor Copy Constructor Assignment operator; After C++11 - Move Copy constructor Move Assignment...
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These rules are instrumental when you design your class. When you create/write a new class, you always think of 5 place holder methods in it. Earlier it was three, but after C++ 11 it became 5. They are: Constructor Copy Constructor Assignment operator; After C++11 - Move Copy constructor Move Assignment operator. Rule of 0 means, your class is designed in a way, such that you don't need any of 1,2,3,4,5 Rule of 3 means, you need 1,2,3 Rule 3 of 5 means, you need all 1,2,3,4,5 Best case is to design a class so that you have a rule of 0. But it's not always possible. It will depend on the nature of your class members. It's bad practice to have them as raw pointers because then you have to write these constructors carefully and also think about resource leakage. Sometimes, we make them shared pointer or unique pointer etc. to reduce our work of writing these constructors and methods. If your class members are themselves following the rule of 0,3,5 etc., then it will also affect your decision whether you have to give all 5 or 0 or 3. In a nutshell, it's always a good practice to think about these five methods, whenever you write a new class. Good question!! read less
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