Question

Consider the following declarations: class bagType { public: void set(string, double, double, double, double); void print() const; string getStyle() const; double getPrice() const; void get(double, double, double, double); bagType(); bagType(string, double, double, double, double); private: string style; double l; double w; double h; double price; }; bagType newBag; //variable declaration a. How many members does class bagType have? b. How many private members does class bagType have? c. How many constructors does class bagType have? d. How many constant functions does class bagType have? e. Which constructor is used to initialize the object newBag?

Short answer

a. 11; b. 5; c. 2; d. 1; e. Default constructor `bagType()`.

Step-by-step solution

Identify Members of the Class

A class's members include both variables (data members) and functions (member functions or methods). The `bagType` class includes member functions `set`, `print`, `getStyle`, `getPrice`, `get`, and two constructors `bagType()`, and `bagType(...)`, as well as the data members `style`, `l`, `w`, `h`, and `price`. In total, this class has 11 members.

Count Private Members

The private section of the `bagType` class includes the data members `style`, `l`, `w`, `h`, and `price`. Thus, there are 5 private members in the class.

Determine the Number of Constructors

A constructor in a class is a special member function with the same name as the class. The `bagType` class has two constructors: the default constructor `bagType()` and the parameterized constructor `bagType(string, double, double, double, double)`. Therefore, there are 2 constructors.

Identify Constant Functions

Constant functions are marked with the `const` keyword. In the `bagType` class, the function `print()` is the only function declared as `const`. Therefore, there is 1 constant function.

Identify Which Constructor is Used for Initialization

When an object of a class is declared without passing any arguments, such as `bagType newBag;`, the default constructor is used for initialization. Thus, the default constructor `bagType()` is used for `newBag`.

Key concepts

Understanding Constructors in C++

Constructors in C++ are special functions that help create and initialize objects of a class. They have the same name as the class and do not return any value. In the given `bagType` class, there are two constructors:

• Default Constructor: `bagType()` is used when an object is created without passing any arguments, like `bagType newBag;`. It ensures that the object is properly initialized with default values.
• Parameterized Constructor: `bagType(string, double, double, double, double)` allows initializing an object with specific values, like a bag with a certain style and measurements.

Using constructors helps protect your program from unexpected behavior by ensuring that your objects start in a valid state.
Constructors automatically get triggered when an object is created, which simplifies the setup process of an object.

The Role of Private Members in C++ Classes

Private members in a C++ class are variables and functions hidden from outside access. You can't access them directly from outside the class. In the `bagType` class, the private members are `style`, `l`, `w`, `h`, and `price`.

• Encapsulation: By keeping these data members private, you encapsulate the data, protecting it from unintended modifications and misuse.
• Controlled Access: As private members, these variables can only be accessed or modified through public member functions, like `set` or `get`, that belong to the class.

This approach maintains the integrity and validity of the data, as any change to these members must happen through the mechanisms defined in the class itself.
In practice, this gives you control over how the data is accessed and modified, thus supporting better software design.

Understanding Constant Functions in C++

Constant functions in C++ are member functions that do not alter the object on which they are called. In the `bagType` class, `print()` is declared as a `const` function.

• Const Keyword: By adding `const` after the function declaration, you ensure that the function cannot modify any data members of the object.
• Read-Only Operations: Constant functions are ideal for performing operations that only need to read data members without the risk of modifying them.

By declaring a function as `const`, it's a signal to other developers that calling this function will not alter the state of the object, which can prevent bugs in your code.
Constant functions contribute to maintaining the stability and reliability of your program's functionality.

Exploring Member Functions in C++ Classes

In C++, member functions are functions that belong to a class and have access to its data members. In the `bagType` class, the member functions are `set`, `print`, `getStyle`, `getPrice`, and `get`.

• Access Methods: Functions like `get` or `getStyle` provide access to the private data members, allowing their values to be retrieved.
• Mutator Methods: Functions like `set` allow for the modification of the object’s private data members, following specific rules defined within the function.

These functions support building robust classes by abstracting the way data is modified or accessed. They provide a controlled interface for interacting with an object’s internal state.
Using member functions effectively causes a class to be flexible and reliable, as it clearly defines how an object's data is manipulated.