Lab: Generic types

Objective

In this lab exercise, you will utilize generic types to refactor given classes that represent items in a library. This refactoring will allow you to understand and apply the principles of generic programming for creating reusable and type-safe code. The transformation from non-generic to generic code will illustrate the adaptability and maintainability of using generic types in a real-world scenario.

Provided code

Carefully review the provided code. Notice how BookItem and MagazineItem share similar structures and functionalities, but they are implemented as separate, distinct classes due to their operation on different types – Book and Magazine. This design can lead to code duplication, which generics can help eliminate by enabling a single class to operate on different types while maintaining type safety.

class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
}

class Magazine
{
    public string Title { get; set; }
    public string Issue { get; set; }
}

class BookItem
{
    public int ID { get; set; }
    public Book Book { get; set; }
    public DateTime AddedToLibrary { get; set; }
    public bool IsCheckedOut { get; set; }
}

class MagazineItem
{
    public int ID { get; set; }
    public Magazine Magazine { get; set; }
    public DateTime AddedToLibrary { get; set; }
    public bool IsCheckedOut { get; set; }
}

The below script needs to be able to find the current output cell; this is an easy method to get it.

Instructions

Step 1: Analyze the code

Reflect on why having separate BookItem and MagazineItem classes might be problematic in terms of code redundancy and maintenance.

🤔 Reflection

How might the use of generic types alleviate the issues identified with the current design?

Step 2: Define a generic class

Create a single generic class LibraryItem<T>, where T can be any type. Include properties that are common between BookItem and MagazineItem, such as ID, Item (of type T), AddedToLibrary, and IsCheckedOut.

Step 3: Implement a method to display item status

Override the ToString() method in LibraryItem<T> and return a string containing the ID, the AddedToLibrary date, and whether the book IsCheckedOut.

🤔 Reflection

How does the implementation of this methods in a generic class compare to implementing them in a non-generic class? How does the addition of new functionality in the generic class illustrate the maintainability and adaptability of generics in software development?

🤔 Reflection

Why is it not possible to access the Title of the book or magazine in a library item? How can we also print the information of the book or magazine in the ToString() method above?

Step 4: Instantiate and use your generic class

Create instances of LibraryItem<T>, using Book and Magazine as type parameters, and interact with them utilizing the method implemented in Step 3. Reflect on the interactions and the versatility provided by the generic class.

LibraryItem<Book> bookItem = new LibraryItem<Book>( /* .... */ );
LibraryItem<Magazine> magazineItem = new LibraryItem<Magazine>( /* .... */ );

Challenge

Experiment by creating more classes representing other items that you might find in a library like BoardGame, EReader, and Tablet. Then show that you can instantiate LibraryItem<T> with these new types. Reflect on the reusability of the generic class with different type parameters.