Chapter 19, Silver Challenge Solution

Swift Programming (3rd Edition) 19. Protocols
1

I first created a Book struct to hold the title, author, and average review score.

// Silver challenge
struct Book {
    let title: String
    let author: String
    let averageReview: Double
}

I then created the BookCollection type as a struct with the TabularDataSource protocol’s required methods. I also made the BookCollection struct conform to the CustomStringConvertible protocol and implemented its required description property. Additionally, I included a mutating function for adding books to the collection, which is represented by an array of type Book.

struct BookCollection: TabularDataSource, CustomStringConvertible {
    var books = [Book]()
    
    var description: String {
        return "BookCollection"
    }
    
    var numberOfRows: Int {
        return books.count
    }
    
    var numberOfColumns: Int {
        return 3
    }
    
    func label(forColumn column: Int) -> String {
        switch column {
        case 0: return "Title"
        case 1: return "Author"
        case 2: return "Average Review"
        default: fatalError("Invalid column!")
        }
    }
    
    func itemFor(row: Int, column: Int) -> String {
        let book = books[row]
        switch column {
        case 0: return book.title
        case 1: return book.author
        case 2: return String(book.averageReview)
        default: fatalError("Invalid column!")
        }
    }
    
    mutating func add(_ book: Book) {
        books.append(book)
    }
}

I finished up with some code to test my new functionality.

var library = BookCollection()
library.add(Book(title: "IT",
                 author: "Stephen King",
                 averageReview: 4.5))
library.add(Book(title: "The Lord of the Rings Illustrated", 
                 author: "J. R. R. Tolkien",
                 averageReview: 5))
library.add(Book(title: "Swift Programming: The Big Nerd Ranch Guide",
                 author: "Mikey Ward",
                 averageReview: 4.6))
printTable(library)

The resulting printout:

Table: BookCollection
| Title | Author | Average Review |
|    IT | Stephen King |            4.5 |
| The Lord of the Rings Illustrated | J. R. R. Tolkien |            5.0 |
| Swift Programming: The Big Nerd Ranch Guide | Mikey Ward |            4.6 |
2

Note: I used a 2-D Array!

print(“------------------SILVER CHALLENGE-----------------”)
class BkClctn : TabularDataSource, CustomStringConvertible
{
var organizationName : String
var description : String
{
return(“(organizationName)”)
}
var books : [[String]]
var numberOfRows: Int
{
return 3
}
var numberOfColumns: Int
{
return 3
}

init(organizationName: String, books: [[String]]) {
    self.organizationName = organizationName
    //self.description = description
    self.books = books
    //self.numberOfRows = numberOfRows
    //self.numberOfColumns = numberOfColumns
}


func label(forColumn column: Int) -> String
{
    if column == 0
    {
        return "  Title  "
    }
    else if column == 1
    {
        return "  Author  "
    }
    else
    {
        return "  Amazon Avg Reviews  "
    }

}

func itemFor(row: Int, column: Int) -> String
{
    return books[row][column]
}

}

// limit is seven
var libKids = [
[“Harry Potter”, “J.K Rowling”, “5.0”],
[“The alchemist”, “Paulo Coelho”, “5.0”],
[“Iron King”, “Julie Kagawa”, “4.0”]
]

let libKidsIns = BkClctn(organizationName: “Fictional Books”, books: libKids)
var printNow = libKidsIns.itemFor(row: 0, column: 0)
print(printNow)
printTable(libKidsIns)