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

Jeff Norton
Jeff Norton
4,366 Points
Posted by Jeff Norton
Jeff Norton
4,366 Points

I don't see how a dictionary that's passed into the initializer can contain both the title and the author.

If dict looks like var dict = ["J.R.R. Tolkien", "Lord of the Rings", "Lloyd Alexander", "The High King"] I don't see how I can pull out values from the dictionary in the initializer method, whether or not it was even a failable initializer. Can you help me see how to do that?

optionals.swift 
struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

}

1 Answer

jcorum
jcorum
71,830 Points

Jeff, your "dictionary" is an array, not a dictionary. See dict1 below.

struct Book {
    let title: String
    let author: String
    let price: String?
    let pubDate: String?

    init?(dict: [String: String]) {  //failable initializer
        guard let title = dict["title"], let author = dict["author"] else {
            return nil
        }

        self.title = title
        self.author = author
        self.price = dict["price"]
        self.pubDate = dict["pubDate"]
    }
}

If you want to test this code in an Xcode playground add these lines after the above struct:

let dict1 = [ "title" : "Pride & Prejudice", "author" : "Jane Austen", "price" : "23.95"]
let b1 = Book(dict: dict1)
b1?.title
b1?.author
b1?.price
b1?.pubDate