Question

Mark the following statements as true or false. a. The constructor of a derived class can specify a call to the constructor of the base class in the heading of the function definition. b. The constructor of a derived class can specify a call to the constructor of the base class using the name of the class. c. Suppose that \(\mathbf{x}\) and \(\mathbf{y}\) are classes, one of the member variables of \(\mathbf{x}\) is an object of type \(\mathbf{y}\), and both classes have constructors. The constructor of \(\mathbf{x}\) specifies a call to the constructor of \(y\) by using the object name of type \(y\)

Short answer

a. True, b. False, c. False.

Step-by-step solution

Analyze Statement a

Statement: "The constructor of a derived class can specify a call to the constructor of the base class in the heading of the function definition." This statement refers to how initializations occur in derived class constructors. In C++, a derived class's constructor can indeed specify a call to a base class constructor in the member initializer list, which is part of the constructor's heading. Thus, statement a is **True**.

Analyze Statement b

Statement: "The constructor of a derived class can specify a call to the constructor of the base class using the name of the class." This statement seems to suggest that the base class constructor is called using the class name itself, similar to how member functions are called. However, in C++, the name of the base class is not directly used during initialization in a derived class's constructor; instead, the member initializer list is used. Thus, statement b is **False**.

Analyze Statement c

Statement: "Suppose that \(\mathbf{x}\) and \(\mathbf{y}\) are classes, one of the member variables of \(\mathbf{x}\) is an object of type \(\mathbf{y}\), and both classes have constructors. The constructor of \(\mathbf{x}\) specifies a call to the constructor of \(y\) by using the object name of type \(y\)." In C++, when a class \(\mathbf{x}\) has a member object of another class \(\mathbf{y}\), the constructor of \(\mathbf{x}\) needs to explicitly call the constructor of \(\mathbf{y}\) in the initialization list, not by the object name. Thus, statement c is **False**.

Key concepts

Derived Class

In C++, a derived class is a class that inherits properties and behaviors from another class, known as the base class. This concept allows for reusable code and organized class hierarchies, making object-oriented programming powerful and efficient. Derived classes can add new features or modify existing ones from the base class. They can be used to create complex structures that still rely on shared functionalities.
When creating a derived class, you often inherit traits of a base class to extend functionality without rewriting existing code. Derived classes can change or extend the behavior and properties of base classes while still using the structure of the base class.

• The syntax for creating a derived class involves specifying the base class during the class definition.
• Derived classes can access public and protected members of the base class.
• Private members of a base class are inaccessible directly through the derived class.

Base Class

A base class in C++ serves as the foundation from which other classes are developed. This class can encapsulate common properties and methods that other classes can use as a template. The base class simplifies code management by grouping shared capabilities that derived classes can leverage.
The base class contains definitions for data and functionalities shared among derived classes, maintaining consistency across derived implementations. It ensures that similar objects can operate on identical methods and have consistent attributes.

• Base classes help in defining the common interface and ensures a structured object-oriented design.
• They contain all the functionalities that should be available to derived classes.
• The base class can also provide default behaviors that can be overridden by derived classes.

Object Initialization

Object initialization in C++ is how resources and values are assigned to newly created objects. This is crucial in constructing objects correctly, especially when working with class hierarchies that involve base and derived classes.
When a derived class is instantiated, it typically calls the constructor of its base class first to ensure that all inherited attributes are correctly initialized. This process is done through a mechanism known as **member initializer lists**. The C++ constructor for the derived class includes a list of initializations for the base class, ensuring that the object is set up correctly.

• Member initializer lists are used in constructors to initialize class data members and base classes.
• If a class contains objects of other types as members, their corresponding constructors must be called as part of this process.
• C++ allows constructors to delegate to other constructors, ensuring proper order and methodology during object construction.