Question

The class Stuff has both a copy constructor and an overloaded = operator. Assume that blob and clump are both instances of the stuff class. For each statement below, indicate whether the copy constructor or the overloaded = operator will be called. \\[ \begin{array}{l} \text { Stuff } b \operatorname{lob}=\text { clump } \\ \text { clump }=\text { blob; } \end{array} \\] blob. operator=(clump) ; showValues (blob); // blob is passed by value.

Short answer

2. Which statement(s) call the overloaded = operator?

Step-by-step solution

Statement 1: Stuff blob = clump;

In this statement, a new instance of the Stuff class named "blob" is being created by initializing it with the value of "clump". This is a case of direct initialization, so the copy constructor will be called here.

Statement 2: clump = blob;

In this statement, the "=" operator is explicitly being used to assign the value of "blob" to the existing "clump" object. Therefore, the overloaded = operator is called in this case.

Statement 3: blob.operator=(clump);

In this statement, the overloaded = operator is called explicitly using the dot operator. So, the overloaded = operator will be called here.

Statement 4: showValues(blob);

This statement is calling a function named "showValues" and passing "blob" as an argument. If "showValues" function takes the argument by value, then the copy constructor will be called to create a temporary object. However, if it takes the argument by reference or pointer, then neither copy constructor nor the overloaded = operator will be called.

Key concepts

Overloaded Assignment Operator

In C++ programming, the assignment operator, denoted by '=', is used to copy values from one object to another already existing object. However, the default behavior may not be suitable for objects that manage resources like dynamically allocated memory or file handles. To cater to such needs, C++ allows the overloading of the assignment operator.

When you overload the assignment operator, you can define how objects of a class should be assigned to each other. This customization is crucial when your class has pointers or non-trivial data structures, ensuring a deep copy of the resources to prevent issues like double deletion or dangling pointers. For instance, if we have an object 'clump' and assign it to an existing object 'blob' using 'blob = clump;', it's the overloaded assignment operator that takes charge to handle this operation efficiently.

C++ Copy Constructor

The C++ copy constructor is a special constructor that initializes a new object using another object of the same class. This comes into play when an object is created by copying another object. For example, if we declare a new object 'blob' by initializing it with an existing object 'clump' using the statement 'Stuff blob = clump;', the copy constructor is called to build 'blob' with the properties of 'clump'.

This particular constructor is essential when the class contains resources that need to be duplicated accurately. The copy constructor makes sure that a deep copy is made if necessary, avoiding issues that occur with a shallow copy, such as shared pointers to the same resource.

Object Initialization

Initializing objects is a fundamental concept in C++ object-oriented programming. Object initialization occurs when you create a new instance of a class. There are several ways to do this in C++, including direct initialization and uniform initialization.

In our exercise example, the statement 'Stuff blob = clump;' is an instance of direct initialization, which invokes the copy constructor. When initializing objects, it's important to consider the resources the object may handle and ensure appropriate constructors are in place, be it a default, copy, or parameterized constructor, to initialize the object's state correctly.

C++ Object-Oriented Programming

C++ is famously known for its support of object-oriented programming (OOP), a paradigm that uses objects and classes to create modular and reusable code. The key features of OOP include encapsulation, inheritance, polymorphism, and abstraction.

Classes serve as blueprints for objects, and when an instance of a class is created, we refer to it as an object. Constructors, including the copy constructor, and operators, such as the overloaded assignment operator, play a crucial role in object lifecycle management. Understanding how and when they are called in operations, like during the initialization of an object or assigning one object to another, is fundamental for writing robust C++ applications.