Question

Consider the definition of the following class: class employee //Line 1 { //Line 2 public: //Line 3 employee(); //Line 4 employee(string, int, double); //Line 5 employee(int, double); //Line 6 employee(string); //Line 7 void setData(string, int, double); //Line 8 void print() const; //Line 9 void updatePay(double x); //Line 10 int getNumOfServiceYears() const; //Line 11 double getPay() const; //Line 12 private: //Line 13 string name; //Line 14 int numOfServiceYears; //Line 15 double pay; //Line 16 }; //Line 17 a. Give the line number containing the constructor that is executed in each of the following declarations: i. employee tempEmployee; ii. employee newEmployee("Harry Miller", 0, 25000); iii. employee oldEmployee("Bill Dunbar", 15, 55000); b. Write the definition of the constructor in Line 4 so that the instance variables are initialized to "", 0, and 0.0, respectively. c. Write the definition of the constructor in Line 5 so that the instance variables are initialized according to the parameters. d. Write the definition of the constructor in Line 6 so that the instance variable name is initialized to the empty string and the remaining instance variables are initialized according to the parameters.

Short answer

a. i: Line 4, ii: Line 5, iii: Line 5 b. `employee::employee() : name(""), numOfServiceYears(0), pay(0.0) {}` c. `employee::employee(string name, int numOfServiceYears, double pay) : name(name), numOfServiceYears(numOfServiceYears), pay(pay) {}` d. `employee::employee(int numOfServiceYears, double pay) : name(""), numOfServiceYears(numOfServiceYears), pay(pay) {}`

Step-by-step solution

Determine Constructor for tempEmployee

The declaration `employee tempEmployee;` invokes the default constructor because no parameters are being passed. Referring to the class definition, the default constructor is on **Line 4**.

Determine Constructor for newEmployee

The declaration `employee newEmployee("Harry Miller", 0, 25000);` uses three parameters: a string, an integer, and a double. This matches the signature of the constructor on **Line 5**.

Determine Constructor for oldEmployee

Similarly, the declaration `employee oldEmployee("Bill Dunbar", 15, 55000);` also uses a string, an integer, and a double. Therefore, this also calls the constructor on **Line 5**.

Define the Default Constructor for Line 4

The default constructor `employee()` should initialize the instance variables `name`, `numOfServiceYears`, and `pay` to `""`, `0`, and `0.0`, respectively. The definition is: ```cpp employee::employee() : name(""), numOfServiceYears(0), pay(0.0) {} ```

Define the Constructor for Line 5

The constructor on Line 5 `employee(string, int, double)` initializes each member variable with its corresponding parameter. The definition is: ```cpp employee::employee(string name, int numOfServiceYears, double pay) : name(name), numOfServiceYears(numOfServiceYears), pay(pay) {} ```

Define the Constructor for Line 6

The constructor on Line 6 `employee(int, double)` initializes the `name` to an empty string and `numOfServiceYears`, `pay` to the provided values. The definition is: ```cpp employee::employee(int numOfServiceYears, double pay) : name(""), numOfServiceYears(numOfServiceYears), pay(pay) {} ```

Key concepts

default constructor

When we create an object in C++ without providing any arguments, we invoke a constructor known as the default constructor. Its primary task is to initialize an object with default values. In the context of the provided exercise, the `employee` class has a default constructor declared on **Line 4**. This constructor initializes the member variables to default values: `name` as an empty string `""`, `numOfServiceYears` to `0`, and `pay` to `0.0`. This ensures that even if we don't pass any information when creating an `employee` object, it still starts with valid, predictable values.
Writing a default constructor is crucial for classes that require initialization, allowing for safe object creation even when no specific data is provided.
Here’s an example of how you can define a default constructor in C++: ```cpp employee::employee() : name(""), numOfServiceYears(0), pay(0.0) {} ```

parameterized constructor

To create an object with initial values specified at the time of creation, we use what is known as a parameterized constructor. This constructor is designed to accept arguments, which are then used to initialize the object’s member variables. In the class `employee` from the exercise, there are several parameterized constructors, yet the one on **Line 5** is notable here.
It allows you to initialize an employee with a `string` for the name, an `int` for the number of years of service, and a `double` for the pay. This provides flexibility in the creation of objects, enabling objects to be instantiated with specific, intended values.
Here’s a sample definition: ```cpp employee::employee(string name, int numOfServiceYears, double pay) : name(name), numOfServiceYears(numOfServiceYears), pay(pay) {} ```This constructor will be called whenever an object is created with three parameters matching these types, ensuring that the object’s members are initialized with the intended starting values.

constructor definition

A constructor definition provides the specific implementation of what the constructor should do when an instance of the class is created. It involves setting up the initial state of an object by establishing values for its member variables. In C++, constructors have the same name as the class and do not have a return type. This distinguishes them from other member functions.
For the `employee` class, different constructors handle different initialization scenarios. For instance, the **default constructor** initializes everything with neutral or empty values, while **parameterized constructors** allow for specific initialization with given arguments. - A constructor is invoked whenever an object is instantiated. - Constructors can be overloaded by having different parameter lists. Here's how you can define a parameterized constructor: ```cpp employee::employee(int numOfServiceYears, double pay) : name(""), numOfServiceYears(numOfServiceYears), pay(pay) {} ```This version of the constructor initializes the `name` with an empty string, while `numOfServiceYears` and `pay` are set to the values passed as parameters.

class member initialization

Class member initialization is a critical aspect of constructors in C++. It enables setting initial values to variables associated with a class object upon its creation. In the `employee` class, the members `name`, `numOfServiceYears`, and `pay` are initialized during object instantiation using a member initializer list.
A member initializer list is a more efficient way to set default values for data members as it initializes them before entering the body of the constructor, potentially reducing processing overhead. In the constructor definitions provided earlier, you might have seen how each member is initialized using a colon `:` followed by the member assignment. - For a **default constructor**, members are assigned neutral values to ensure a valid initial state. - For a **parameterized constructor**, members are initialized with the provided argument values, granting the object specific traits from the start.
This approach enhances performance and reliability in object-oriented programming. Here’s how it looks: ```cpp employee::employee() : name(""), numOfServiceYears(0), pay(0.0) {} ```This snippet illustrates a member initializer list in action, showing efficient initialization of the class members.