Question

Modify class Employee in Figs. 13.613.7 by adding a private utility function called isValidSocialSecurityNumber. This member function should validate the format of a social security number (e.g., #--, where # is a digit). If the format is valid, return true; otherwise return false.

Short answer

Add isValidSocialSecurityNumber function to validate SSN format: ###-##-####.

Step-by-step solution

Understand the Format

First, we need to understand the format of a valid Social Security Number (SSN), which is ###-##-#### where each '#' is a digit (0-9). The SSN should therefore have exactly 11 characters, including two hyphens ('-') present at the 4th and 7th positions.

Define the Function

Create a private member function within the Employee class named 'isValidSocialSecurityNumber'. This function will accept a string argument, representing the SSN to be validated.

Check Length

In the function, first check that the length of the SSN string is exactly 11 characters. If not, return false immediately since the format would be invalid.

Check Hyphen Positions

Verify that the characters at positions 3 and 6 are hyphens ('-'). If not, return false, as this would also indicate an invalid format.

Check Digits

Ensure that all other characters (positions 0-2, 4-5, and 7-10) are digits. You can use a loop or individually check each position. Return false if any non-digit character is found in these positions.

Return True if Valid

If all checks pass, it means the SSN is in the correct format. Therefore, return true at the end of the function, indicating a valid SSN.

Key concepts

Object-Oriented Programming

Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects". Objects can contain data, in the form of fields often known as attributes, and code, in the form of procedures often known as methods. OOP helps to manage complex software systems through:

• Encapsulation: This means wrapping the data (fields) and code (methods) together into a single unit, or class. It helps protect the internal state of an object from the outside world.
• Abstraction: Simplifying complex reality by modeling classes based on the overall behavior as compared to if you had not made an abstraction.
• Inheritance: Allowing objects or classes to inherit properties and methods from another class. This promotes code reusability and logical hierarchy.
• Polymorphism: The ability to present the same interface for different data types. This is useful in allowing one class to be used for a general class of actions.

When implementing the Employee class mentioned in the exercise, OOP aids in managing complex systems by creating well-structured code that's both reusable and easy to maintain.

Class Design

Designing a class involves deciding on what data attributes should be included and what member functions are necessary. A well-designed class encapsulates all the data and behaviors that belong to the entity it models. While designing the Employee class:

• Include clear and concise attributes like the name, ID, and social security number (SSN).
• Member functions that perform tasks, for example, a function to validate the SSN.
• Use access specifiers like private to protect sensitive data and functions that should not be accessed directly from outside the class.

Good class design also pays attention to efficiency and the class's responsibilities. For instance, splitting large functions into smaller, more manageable ones that only hold one responsibility, such as the 'isValidSocialSecurityNumber' function for SSN validation.

Data Validation

Data validation refers to the process of ensuring data is accurate and meets certain criteria before it's processed further. In programming, this ensures that the input meets the expected format and value ranges. Effective data validation can:

• Prevent data errors that could occur due to user's accidental or intentional incorrect input.
• Help maintain data integrity within the system.
• Provide clear communication to users when input doesn’t meet required standards.

In the Employee class, data validation is crucial for fields like the social security number. By applying checks on the length, structure, and character type—like what is performed in the 'isValidSocialSecurityNumber' function—you ensure that only valid SSNs are accepted, safeguarding against potential errors or mismanagement of employee data.

Member Function

Member functions, also known as methods, are functions defined within a class that operate on the data contained in an object of that class. These functions are the core part of encapsulating behavior within objects. Member functions can:

• Modify the state of an object—such as updating a field or attribute.
• Access data within the object, using getter and setter methods.
• Execute specific operations, like the 'isValidSocialSecurityNumber' function within the Employee class, which is tasked with verifying the format of the SSN.

The design of member functions is integral to the functionality of the class. They should be kept modular, specific to a task, and when possible, made private to avoid unintended interactions from outside code. In the context of the exercise, the validity check function is an excellent example of a utility member function that adds significant value to the integrity of data used within the class.