Classes + Inheritance

What is the difference between a class and a struct in C++?

In C++, a class and a struct are similar, but the default access specifier differs: in a class, members are private by default, while in a struct, they are public by default.

What is multiple inheritance, and how can it be managed in C++?

Multiple inheritance occurs when a class inherits from more than one base class. It can be managed using virtual inheritance to solve ambiguity and the diamond problem, ensuring a single instance of the common base class.

How do you initialize a base class in a derived class constructor?

A base class can be initialized in a derived class constructor's initializer list. Example: DerivedClass() : BaseClass(param) {}

How can you explicitly call a base class's constructor from a derived class?

A base class's constructor can be called explicitly from a derived class's initializer list. Example: DerivedClass() : BaseClass(param) {}

How can you prevent a class from being instantiated in C++?

A class can be prevented from being instantiated by making its constructor private or protected, or by making it an abstract class with pure virtual functions.

How do you use a base class's member function in a derived class?

A derived class can call a base class's member function using the scope resolution operator (BaseClass::functionName()) or by invoking it directly if it is accessible.

What is a virtual base class, and why is it used?

A virtual base class is a base class that is shared among multiple derived classes in a diamond inheritance scenario to avoid multiple instances of the base class and ensure a single, consistent instance.

What is the purpose of a virtual destructor?

A virtual destructor ensures that the destructor of the derived class is called when an object is deleted through a pointer to the base class. This prevents resource leaks and undefined behavior.

What is the purpose of the virtual destructor in a base class?

A virtual destructor ensures that when a base class pointer is used to delete a derived class object, the derived class's destructor is called, allowing proper resource cleanup and preventing resource leaks.

What is an abstract base class in C++?

An abstract base class is a class that contains at least one pure virtual function. It is meant to be used as a base class and cannot be instantiated directly.

What is an interface in C++, and how does it relate to pure virtual classes?

An interface in C++ is a class that contains only pure virtual functions and no data members. It defines a contract that derived classes must implement. Pure virtual classes are used to create interfaces.

How do you declare and define a class method that can be used without an object?

Declare the method as static within the class. It can be defined and called using the class name without needing an instance of the class. Example: cppCopy code class MyClass { public: static void staticMethod(); };

How do you implement the copy constructor and assignment operator for a class with dynamic memory?

Implement the copy constructor and assignment operator to perform deep copying of dynamically allocated memory to avoid issues like double deletion. Example: cppCopy code class MyClass { public: MyClass(const MyClass& other); // Copy constructor MyClass& operator=(const MyClass& other); // Assignment operator ~MyClass(); // Destructor private: int* data; };

What is the difference between public, protected, and private inheritance?

Public inheritance: Base class's public and protected members remain public and protected in the derived class. Protected inheritance: Base class's public and protected members become protected in the derived class. Private inheritance: Base class's public and protected members become private in the derived class.

How does public inheritance differ from protected inheritance in terms of base class member accessibility?

Public inheritance: The base class's public and protected members remain public and protected in the derived class. Protected inheritance: The base class's public and protected members become protected in the derived class, restricting their accessibility.

What is the difference between a shallow copy and a deep copy of a class?

Shallow copy: Copies the values of data members, including pointers, but does not duplicate the objects pointed to. Deep copy: Creates copies of objects pointed to by pointers, ensuring each object has its own copy of dynamically allocated resources.

What is the difference between static and non-static member functions?

Static member functions: Can be called without an object and do not have access to the instance's data members. Non-static member functions: Require an object to be called and have access to the instance's data members.

What is the class keyword used for in C++?

The class keyword is used to define a class, which is a user-defined data type that includes attributes (data members) and methods (member functions) encapsulated within a single entity.

How do you use the dynamic_cast operator in C++?

The dynamic_cast operator is used for safe downcasting of pointers or references to base and derived classes. It checks at runtime whether the cast is valid and returns a null pointer if it fails.

What is the final keyword used for in C++?

The final keyword indicates that a class cannot be inherited from, or a virtual method cannot be overridden further in derived classes. It helps to enforce design constraints and optimize performance.

What is the override keyword used for in C++?

The override keyword specifies that a method is intended to override a virtual method in a base class. It helps the compiler catch errors if the method does not match the base class's method signature.

What is the purpose of the protected access specifier in inheritance?

The protected access specifier allows derived classes to access the base class's members, but prevents access from outside the class hierarchy. It supports controlled exposure of class members.

What is the purpose of the static keyword in a class?

The static keyword indicates that a member belongs to the class itself rather than to any particular object. Static members are shared across all instances of the class and can be accessed using the class name.

What is the use of the virtual keyword in a destructor?

The virtual keyword in a destructor allows derived class destructors to be invoked correctly when deleting an object through a base class pointer, ensuring proper cleanup of derived class resources.

What is the difference between override and final in C++?

override: Specifies that a method is intended to override a virtual method in a base class. final: Indicates that a method cannot be further overridden or a class cannot be inherited.