C++ Base Class Constructor Rules: Understanding the Basics

As a programmer, it is important to understand the basics of C++ Base Class Constructor Rules. In object-oriented programming, classes can be derived from other classes, which are called base classes. When a derived class is created, the constructor of the base class is called automatically. But what are the rules for base class constructors?

  1. Default Base Class Constructor
  2. Explicit Base Class Constructor Call
  3. Order of Base Class Constructor Calls
  4. Conclusion

Default Base Class Constructor

If a base class constructor is not specified, the default constructor is called. This is a constructor that takes no arguments. If the base class does not have a default constructor, then the derived class constructor must explicitly call the base class constructor with arguments.

Explicit Base Class Constructor Call

If a base class constructor is specified, the derived class constructor must explicitly call it. This is done using the base class name followed by the constructor arguments in parentheses. For example:

DerivedClass::DerivedClass(int x) : BaseClass(x) {
    // Constructor code

This calls the constructor of the BaseClass with the argument x.

Order of Base Class Constructor Calls

If a derived class is derived from multiple base classes, the constructor for each base class is called in the order they are listed in the derived class definition. For example:

class DerivedClass : public BaseClass1, public BaseClass2 {
    DerivedClass(int x, int y) : BaseClass1(x), BaseClass2(y) {
        // Constructor code

In this case, the constructor for BaseClass1 is called before the constructor for BaseClass2.


Understanding the C++ Base Class Constructor Rules is crucial for writing effective object-oriented code. By following these rules, you can ensure that constructors are called in the correct order and that your code is structured properly.

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