Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community!

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Swift 2.0 Enumerations and Optionals Introduction to Optionals Initializing Optional Values

Benjamin Lim
Benjamin Lim
2,747 Points

I understand most of this, but will someone explain the last part?

This is the correct answer in which i got from another post on the forum. I understand most of this up till it says self.price = dict["price"] self.pubDate = dict["pubdate"]

Why do we have to specify those strings?


struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?
    init?(dict: [String: String]) {

    guard let title = dict["title"], author = dict["author"] else {
    return nil
    self.title = title
    self.author = author
    self.price = dict["price"]
    self.pubDate = dict["pubDate"]


1 Answer

You're accessing those values through the keys.

//for example
var dict: [String: String] = ["price": "$1.99", "pubDate": "1999"]
//returns "$1.99"